WASHINGTON — President Barack Obama's pick to run the Pentagon said Wednesday he's inclined to back increased U.S. assistance to Ukraine, including lethal arms, to fight anti-government rebels backed by neighboring Russia.

The White House is reconsidering its opposition to giving Ukraine defensive weapons and other lethal aid to help its struggling military repel the insurgents backed by Moscow. That would be a possible escalation that has been strongly supported by many members of Obama's national security team, but it also would risk turning Ukraine into a proxy war with Russia.

Ashton Carter also said that Russia's military moves in Ukraine are "a clear violation" of a 1994 commitment that Russia made to respect the sovereignty of the newly independent Ukraine as part of Ukraine's agreement to give up the nuclear weapons it inherited from the former Soviet Union.

The so-called Budapest Agreement "provided for Russia to respect the territorial integrity of Ukraine, which it's obviously not done," Carter told members of the Senate Armed Services Committee at his confirmation hearing. "And that is part of the climate and context in which the Ukrainians agreed to give up nuclear weapons in the first place."

Carter said the United States also committed as part of that 1994 deal to "respect but also assure ... the ability of Ukraine to find its own way as an independent country. That is at stake today."

Carter also told committee members that he will seek better use of taxpayer dollars but that Congress must bring stability back to the military's budget. He pledged to fight sexual assaults in the military services and fight against wasteful spending practices.

"The taxpayer cannot comprehend, let alone support, the defense budget when they read of cost overruns, lack of accounting and accountability, needless overhead and the like," he said.

Nominated to be the fourth Pentagon chief of an Obama administration now in its 7th year, Carter faced questions about Iraq, Afghanistan, the Islamic State, the Guantanamo Bay military prison, Russia and other hot spots during his Senate appearance. His confirmation is widely expected, yet members of the committee used the heavily attended hearing to challenge and criticize Obama's foreign policy decisions.

Committee Chairman John McCain, R-Ariz., asked whether Obama was trying to move U.S. troops out of Afghanistan at too fast a clip. McCain has repeatedly questioned the wisdom of setting and announcing a hard end date to the U.S. presence in Afghanistan.

Carter said he would consider changing plans for withdrawing all U.S. troops from Afghanistan by the end of 2016 if security conditions worsen. About 10,600 U.S. troops remain in Afghanistan.

Carter also said he is aware of reports that Islamic State militants may try to expand into Afghanistan, and that he will work with coalition partners to ensure that does not happen.

Carter said he agreed with McCain's assessment that Iran was exploiting turmoil in the Middle East, and said the fight against Islamic extremists who are members of the Islamic State would be a top priority. McCain wasn't satisfied.

"What's the strategy?" McCain asked Carter, before going into questions on Syria and Iraq. .

Carter said the strategy needs to be a lasting one that ensures that the Islamic State will stay defeated — once it is. In Iraq, that job falls to the Iraqi security forces, Carter said. In Syria, the U.S. and its allies are trying to build a moderate force to keep them defeated.

"It doesn't sound like a strategy to me," McCain replied.

But during a recess to give a breather to Carter, who is recovering from back ailments, McCain predicted that the committee would vote to confirm him before a congressional recess scheduled to begin Feb. 16.

In his opening remarks, McCain praised Carter as an honest, hard-working and respected defense professional, and said he hoped he would push back on any attempt by the White House to micromanage the Defense Department, or over-centralize U.S. foreign and defense policies.

McCain used his opening statement to blast what he called the "mindless mechanism of sequestration" — automatic spending cuts that are squeezing the Pentagon budget.

"Despite the growing array of complex threats to our security, we are on track to cut $1 trillion out of America's defense budget by 2021," said McCain. "Readiness is falling across the services, and morale is falling right along with it."

"Army and Marine Corps end-strength is dropping dangerously low. The Air Force is the oldest and the smallest it has ever been. The Navy's fleet is shrinking to pre-World War I levels," said McCain, a Vietnam era prisoner of war.

Carter, a native of Philadelphia, served twice previously in Obama's Pentagon, most recently as deputy defense secretary from 2011 to 2013. He was assistant secretary of defense for international security policy during the administration of President Bill Clinton.

Carter, 60, is a physicist by training and a highly regarded thinker on strategy, budgets and policy. When Obama announced his nomination on Dec. 5, the president credited Carter with a "unique blend of strategic perspective and technical know-how." He is steeped in the intricacies of missile defense, U.S. nuclear weapons, U.S.-China relations and the evolution of North Korea's nuclear program.

Less clear is whether Carter will find more success than Hagel with Obama's inner circle. The president's relationship with the Pentagon has often been strained, with some officials in the department saying Obama views the military skeptically and centralizes decision-making.