Stockholm - President Barack Obama took his campaign for a punitive military strike against Syria overseas on Wednesday, declaring that "the international community cannot be silent" and that its credibility is on the line, as his request for congressional approval of such action moved ahead in the Senate.

But Obama faced fresh resistance from Russia, Syria's stalwart patron, as President Vladimir Putin asserted that the West's case against Syrian President Bashar Assad with respect to his regime's alleged chemical weapons attack on civilians is "absurd" and does not stand up to scrutiny.

In Washington, the Senate Foreign Relations Committee backed military action after two days of hearings Wednesday, but not before changing the text to stress the goal of strengthening Syrian rebels and weakening Assad.

The full Senate could vote as soon as next week on an authorization that now expressly prohibits any U.S. troops in Syria and gives the president a 90-day window to complete military action. The House separately is considering a similar resolution.

Obama will make a major push to marshal global support for a U.S.-led retaliatory strike against Syria once he arrives in St. Petersburg today for the Group of 20 economic summit hosted by Putin. The challenge he faces came into stark relief here Wednesday, however, when Swedish Prime Minister Fredrik Reinfeldt said after meeting with Obama that his small nation could not support a unilateral response.

"At what point do we say we need to confront actions that are violating our common humanity?" Obama said at a news conference in Stockholm. "I would argue that when I see 400 children subjected to gas, over 1,400 innocent civilians dying senselessly . . . the moral thing to do is not to stand by and do nothing."

Obama said responsibility fell upon Congress and the world to retaliate against the Syrian regime for its "horrific" use of chemical weapons.

"I didn't set a red line," Obama told reporters. "The world set a red line when governments representing 98 percent of the world's population said the use of chemical weapons is abhorrent and passed a treaty forbidding their use, even when countries are engaged in war. Congress set a red line when it ratified that treaty."

Obama and his administration have said Assad is directly responsible for the alleged sarin gas attack on hundreds of civilians in the suburbs of Damascus on Aug. 21. But Putin said Syria poses no threat to the United States. He also said he is skeptical of U.S. intelligence, going so far as to accuse Secretary of State John Kerry of lying in his testimony this week to Congress.

"It ought to be convincing," the Russian leader told the Associated Press in an interview published Wednesday. "It shouldn't be based on some rumors and information obtained by the special services through some kind of eavesdropping, some conversations and things like that.

Putin also said he finds it unlikely that Assad would risk international repercussions by using long-banned chemical weapons to kill men, women and children.

At a meeting of the presidential human rights council in Moscow on Wednesday, he accused the U.S. Senate of "legitimizing aggression" and added: "We have all glued ourselves to TV screens and are waiting to see whether there will be a sanction or not. What we should be talking about is that this is absurd in principle."

Russia has so far blocked proposals for U.N. Security Council action against Syria. In the AP interview, Putin warned the United States against launching a unilateral strike against Syria and said Russia is developing a plan of action in case it does so without U.N. approval, although he declined to go into specifics.

Yet he also said that if the United States and its allies could provide sufficient evidence that Assad's forces carried out the Aug. 21 attack, Russia would consider allowing U.N. action against Syria. He added that Russia has frozen the shipment of certain parts for S-300 anti-aircraft missiles that it had agreed to sell to Assad's regime.

In his visit to Stockholm - a trip the White House hastily arranged after Obama called off a Moscow meeting with Putin planned for this week - Obama addressed the strained U.S.-Russia relations, admitting that he and Putin have "hit a wall." He said Russia has failed to acknowledge "some of the terrible behavior of the Assad regime" and is preventing the kind of political transition in Syria that could stabilize the war-torn Middle East country.

Obama made an indirect reference to Russia's controversial new law criminalizing "homosexual propaganda," which has drawn attention ahead of the G-20 summit. "Our gay and lesbian brothers and sisters must be treated equally under the law," he said, adding, "Our societies are strengthened and not weakened by diversity."

At the G-20 summit, Obama has no meeting planned with Putin, but he has scheduled bilateral meetings with British Prime Minister David Cameron, French President Francois Hollande and Japanese Prime Minister Shinzo Abe. U.S. officials said he plans to press his case on Syria in those sessions.

The resolution approved by the Senate committee Wednesday also requires the White House to plan for a way to end the war in Syria through diplomatic means but suggests the administration's goal of a negotiated settlement for Syria is untenable now. Military action should focus on "decisive changes to the present military balance of power" in Syria's civil war, the key panel said.

The panel voted 10 to 7, with seven Democrats joined by three Republicans in favor, while two Democrats joined five Republicans in voting no. Edward Markey, D-Mass., the Senate's newest member, voted "present."

White House press secretary Jay Carney welcomed the vote and praised senators for coming together across party lines.

Three Republicans, Sen. Bob Corker of Tennessee, along with Arizona Sens. Jeff Flake and John McCain, voted with the Democratic majority.

But the vote exposed deep divisions in both parties and demonstrated how the possibility of military engagement in Syria has scrambled political allegiances unlike other issues in recent years. Two of the committee's most liberal members-Sens. Tom Udall, D-N.M., and Christopher Murphy, D-Conn.-joined five conservatives in opposition, including Sens. Marco Rubio, R-Fla., and Rand Paul, R-Ky., who are considered leading GOP presidential contenders in 2016.

During a separate hearing in the House, Kerry said some Arab states are among more than 30 nations supporting U.S. military strikes, even though the Arab League declined to back that option last month. A few Arab states even offered to pay for the military operation, Kerry said.

Offers have been "quite significant, very significant," Kerry said, but he did not name the would-be donors.

The Obama administration is likely to have more difficulty winning passage in the House, where both liberal and libertarian opposition to military engagement is stark. Kerry had an angry exchange with Rep. Jeff Duncan, R-S.C., over what Duncan said was a rash decision to attack.

"Is the power of the executive branch so intoxicating that you have abandoned past caution in favor of pulling the trigger on a military response so quickly?" Duncan asked Kerry.

Kerry, who fought in Vietnam in the 1960s and voted to authorize the war against Iraq a decade ago, shot back angrily: "I volunteered to fight for my country, and that wasn't a cautious thing to do when I did it." When Duncan interrupted, Kerry raised his voice.

"I'm going to finish, congressman," Kerry said.

Earlier, anti-war demonstrators sitting behind Kerry held their red-painted palms aloft for the television cameras. As he did when addressing senators on Tuesday, Kerry acknowledged demonstrators and said their views are welcome. He promised that the administration is not rushing to war.

Testifying alongside Kerry, Joint Chiefs of Staff Chairman Gen. Martin Dempsey said Assad might respond to a missile strike with a retaliatory cyberattack. The Pentagon has planned for that and other possible aftereffects, Dempsey said.

The U.S. government has sent out a classified bulletin alerting certain sectors of industry of the potential for a cyberattack in retaliation for a U.S. missile strike in Syria, according to U.S. and industry officials.

"Those acting on the Syrian government's behalf have already demonstrated a limited capability in cyber," said a senior military official, referring to attacks by the Syrian Electronic Army, a pro-Assad hacker group, that disrupted the public websites of Twitter and The New York Times last month. The official spoke on the condition of anonymity to describe military planning.

Obama, the first sitting U.S. president to visit Sweden for bilateral meetings, came here to discuss trade issues, global development and climate change with a key European ally. But the situation in Syria hung over his visit. Obama pressed his argument for retaliatory strikes by invoking the Holocaust to warn of the consequences of inaction.

Later in the day, he donned a white yarmulke and visited the Great Synagogue and Holocaust Memorial, where he marked the start of the Jewish Rosh Hashanah holidays and paid tribute to the late Swedish humanitarian Raoul Wallenberg, who helped save hundreds of Hungarian Jews during World War II.

Englund reported from Moscow. Washington Post staff writers Anne Gearan, Ed O'Keefe and Ellen Nakashima in Washington contributed to this report.