It remains possible, if not probable, that the world can persuade Iran, through diplomatic means, to end its nuclear-arsenal ambitions.

This weekend came the announcement that Iran had agreed to meet the conditions of a tentative deal announced in November that would effectively freeze Iran's nuclear arms' program for six months, providing time for negotiations on a permanent agreement.

Iran agreed to stop enriching uranium beyond 5 percent, well below the level necessary for developing weapons. Its stockpile of weapons-grade uranium - 20 percent enriched - must be diluted or converted to oxide. It cannot install any new centrifuges.

In return, the United States and the other countries involved in the talks - Britain, Russia, China, France and Germany - agree to lift some sanctions, providing relief estimated at $6 billion to $7 billion. This consists in large part of releasing Iranian oil revenue now frozen in foreign banks. Most economic sanctions remain in place.

The agreement also provides for the outside inspectors that will be necessary to confirm Iran's compliance.

Congress should let Secretary of State John Kerry and the administration test the waters with this interim deal. Some lawmakers, led by Republicans but including Democrats, want to add more sanctions against Iran, which would kick in if Iran violates the accord or no final deal is reached. Such an action by Congress could unravel the deal. Reportedly, hardliners in the Iranian government are complaining that Iran gave too much away. If Congress were to pass more sanctions, it would strengthen the position of these Iranian hardliners that the American government cannot be trusted.

In any case, there is no need for congressional action now. If Iran reneges on its promises it should become apparent soon enough and the United States can again dial up the sanctions and prepare a military option.

This effort to reach a final agreement is well worth it, however unlikely the chances that Iran will abandon its desire to become a nuclear power. President Obama said earlier that, at best, there is a 50-50 chance of reaching a final deal. In reality, it is probably considerably less than that.

While an attack on Iranian nuclear-production facilities may in the end be the only option left, forgoing this attempt to avoid that outcome would be a mistake. The tinder is especially dry now in the Middle East. How things would play out after such an attack is difficult to predict, but it is quite possible an Iranian military response could target neighbors, expand the conflict, disrupt oil supplies and damage the global economy.

An argument can be made that the United States and its allies should not be making any deal with Iran now, given that country's increased meddling, such as providing direct military assistance to President Assad's forces in Syria - who the United States wants out - and working to destabilize Yemen and Bahrain.

However, the tactic to insulate the nuclear negotiations from Iran's other malevolent intentions is the right one. No priority in the region is higher than stopping Iran from getting a nuclear weapon, preferably peacefully by achieving a final deal. While that effort continues, the United States must work in parallel fashion to counteract Iran's efforts to expand its regional influence.

It is possible, perhaps even likely, that Tehran is playing games, stalling with the intention of making a race to develop a bomb after it walks away from talks on a final deal, keeps delaying, or inspectors find it cheating. If that proves true, the United States and allies must act decisively to punish the Iranian regime.

This temporary agreement provides the chance, at least, that Iran will surprise the world and end its weapons' program.