The Obama administration assumes that it needs Russia to get an Iranian nuclear deal. But behind-the-scenes happenings suggest that Russia has its own plans. That may explain why the administration is willing to bypass Congress to get a pact with Tehran.

Russia and Iran have been moving closer in recent months. On Jan. 20, they signed a military cooperation agreement after the first visit of a Russian defense minister to Iran in 15 years. They have agreed to share intelligence and operate joint facilities on the Syrian-Lebanese border, and both nations support Syrian President Bashar Assad. These come on top of existing agreements and ongoing Moscow-Tehran talks over nuclear technology, trade, energy and arms sales.

There are signs that Russia and Iran’s relations are about to get even closer. One of Ayatollah Ali Khamenei’s top advisers, Ali-Akbar Velayti, visited Moscow in late January, and a visit to Tehran by Russian President Vladimir Putin appears to be in the offing. Leaders in both countries seem to be thinking of bigger things.

What is driving interest in warmer relations is obvious. Russia and Iran share strategic hostility to the U.S., with some in Moscow going so far as to suggest an anti-American strategic alliance with Iran. Putin adviser Sergey Glazyev recently said that “a world war is beginning with the aggression of the USA against Russia in Ukraine and against Iran and Syria in the Middle East.” Mr. Glazyev is a hard-liner known for incendiary statements, but he is also close to Mr. Putin and clearly has his ear on Ukraine. Given how aggressive the Putin strategy there has become, these statements should not be ignored.

So what are the implications of a Russian-Iranian alliance?

For one thing, beware of Moscow’s endgame on the Iranian nuclear talks. If Iran gets a one-year breakout potential along with lifted sanctions, it would suit Moscow’s interests perfectly by making its new BFF the region’s biggest power player and giving it increased access to Iran’s expanding quasi-empire that includes Shiite Iraq, Syria, Lebanon and Yemen.

For another, Moscow becomes the kingmaker in deciding the fate of an Iranian nuclear deal. One of the first things Russia could do is to ask the United Nations Security Council to codify the agreement and lift sanctions on Teheran. Having already signed off on the deal, the Obama administration would have to go along.

That may very well have been Mr. Obama’s endgame all along. As Harvard law professor Jack Goldsmith suggests, if the terms of a P5+1 agreement is folded into a Security Council resolution, it would be binding on the U.S. as a matter of international law. As was done in the Libya war resolution, going directly to the United Nations lets Mr. Obama bypass Congress, effectively going over the heads of the American people to cut a binding deal with the “international community.”

If this happens, and Iran decides to cheat on the deal, it will be the United Nations tying America’s hands, not Iran‘s. It would be exceedingly difficult to reimpose U.N. sanctions on Iran, and if the U.S. did so unilaterally, it would stand accused by at least Iran, Russia and China of violating international law. Iran could very well get a nuclear weapons program under the nose of the world, and short of war, the U.S. would be out of options.

This situation suits Russia just fine. Moscow, not Washington, becomes the key decider of whether Iran does or does not acquire nuclear weapons. Russia may now prefer that Iran not get them, but in the future Moscow’s interest in enhancing its strategic position in the Middle East may trump its current caution.

If Washington is not careful, a nuclear Iran may be only the beginning. We also could see the rise of an anti-American axis comprising Iran and Russia, both determined to see the U.S. driven out of the Middle East.

 - A former assistant secretary of state, Kim R. Holmes is a distinguished fellow at The Heritage Foundation