Last week was the biggest news week of the year. Israel invaded Gaza. A passenger jet was shot down, almost certainly by Vladimir Putin's shadow army in Eastern Ukraine. And thanks to a Friday night news dump, the event with probably the greatest long-term impact on us largely escaped attention. That would be the kicking of the can down the road on nuclear talks between Iran, the U.S., and five other world powers.

All of these events are connected in a dangerous and potentially destabilizing way. Twenty-four hours after the Malaysia Airlines jet with at least one American passenger was downed, a grim-faced President Obama came into the White House briefing room to declare it an outrage. Obama, who jacked up sanctions on the Russians the day before the downing of Flight 17, said even more sanctions on Moscow may be in the cards.

Make no mistake about who did this. The missile that knocked the plane down came from territory controlled by Putin's henchmen. The same goons who bragged three weeks ago about having such missiles, and who were heard on radio intercepts Thursday (thanks NSA!) saying they just shot down a plane. Obama is right: The Russians need to be punished.

But here's the problem. Obama has made a nuclear deal with Iran his number one foreign policy goal. But to get Iran to halt its efforts to develop a nuclear weapon, he needs help, on some level, from the Russians. How far can Obama squeeze Putin on Ukraine when he needs his cooperation on Iran?

The Russians have minimal incentive to cooperate. They have big commercial interests in Iran — billions of dollars are at stake in oil and gas deals, and nuclear reactors (to produce electricity, Moscow and Tehran claim). Both Russia and Iran have been hit by American sanctions, their economies are struggling, and they need each other.

It's noteworthy that after Obama and Putin spoke on Thursday (Putin told the president he's unhappy about the new sanctions), Putin made anther call, to Iranian President Hassan Rouhani. "Mr. Putin and Mr. Rouhani exchanged views on the state of talks on Iran's nuclear program," the Kremlin press release said. "The two leaders also examined bilateral cooperation matters of mutual interest, including joint projects in the oil and gas sector and in peaceful nuclear energy."

Putin is in prime position here to gum up the works — he can influence the course of these nuclear talks with Iran, slow them down, even derail them. If he can protect Russian business interests in Iran while sticking it to Obama, why wouldn't he?

So far he hasn't, at least not that much. Iran has made nuclear concessions in the past year and Russia has assisted in the removal of chemical weapons from its other Mideast ally, Syria — easing at least one of many ongoing threats to Israel. Still, Syrian butcher Bashar al-Assad — supported by Hezbollah, which is supported by Iran, which is supported by Russia — is still in power. At the top of this hideous food chain, behind the red-brick walls of the Kremlin, is Putin himself. If he decides that he's being pushed too far by Obama, this type of cooperation could evaporate in a hurry. He can squeeze us on Iran, and he can increase the regional threat to Israel.

For all of Obama's talk, he knows this. The world is vastly less stable today than a week ago, and it was less stable a week ago than it was six months ago. His choice: squeeze Putin, punish him over Ukraine and contain him, Cold War style — or somehow get him to help on Iran. He really can't have it both ways.