The intensified military buildup in the Persian Gulf poses dangers for escalation, both inadvertent and deliberate, around the Iran crisis. Last week's Iranian decision to surround a British naval vessel and seize 15 British sailors and marines directly increases tensions in the Iran conflict (around both the nuclear issue and Iran's intervention in Iraq).

It's possible, though unlikely, that the British sailors were inadvertently in Iranian territory; though certainly the patrols around Iraqi offshore terminals and shipping lanes routinely bring British naval vessels right to the edge of Iranian territorial waters. (The Iraqi sea lane is quite narrow in the area of the conflict with some 200 meters of navigable water in Iraqi territory.) Whatever the case, the well-orchestrated Iranian "surround and seizure" had been planned for some time. It strikes me as a response to the United States holding of Iranian diplomats taken in Irbil several months ago-a deliberate and carefully calibrated escalation, with very limited risk for an outbreak of hostilities. Hence the extraordinary and high-level Iranian military presence quickly marshaled to the scene.

The timing of the event was surely intentional, a provocation right before the Security Council was to vote on further sanctions against Iran. The decision could only have been taken with the approval of Iranian supreme leader Ali Khamenei. President Mahmoud Ahmadinejad would not have been allowed to take the lead on such a decision. The move further confirms that Tehran is not looking for a "diplomatic out." rather it is sending a message to the international community that Iran is prepared for a fight if necessary and that its only remaining options are increasingly unpalatable.

The Iranian decision to take British (rather than American) soldiers suggests that Tehran does not intend to release the troops immediately (though certainly they will remain safe and well looked after), but rather to use them as leverage for negotiations with British diplomats. The lack of direct channels of negotiations between Iran and the United States would have precluded this option with U.S. soldiers and could have led to significant retaliation against Iran. The most likely next step is for Iran to demand the release of its captured diplomats, and conceivably of its government property, in Iraqi territory. That's an unlikely outcome. The incident has the capacity to significantly cool British willingness to support efforts at continued negotiations with Iran on the nuclear conflict, as well as end Iranian participation in the broader "contact group" with the United States and Britain (among others) on Iraq. And both Britain and the United States will now step up their military presence along the edge of Iran's territorial waters, with more frequent and larger-scale patrols. That will heighten the risk of military miscues but reduce the likelihood of any surprise Iranian naval presence.

If anything, the United States and Britain took advantage of the Iranian move to push up the vote on a second resolution against Iran at the Security Council. The sanctions remain extremely limited. And as I've suggested above, they will have no effect on Iranian decision-making. Still, it's worth noting that supreme leader Khamenei last week expressed Iranian intentions to proceed with "illegal" nuclear activities following any further "illegal" sanctions enacted against Iran. The importance of that statement, given IAEA documentation that Iran's nuclear program is progressing, is that it provides greater justification for broader provocative moves against the Islamic Republic and plays into the Israeli argument for the need for an attack.

I still see Israeli security concerns as the most significant driver of likely military action. A series of Israeli war drills last week, including simulated missile attacks on Israeli urban centers and on the main Tel Aviv power station, are particularly noteworthy.

A final point. The Congress continues to push a broad spectrum of legislation against Iran, with strong bipartisan support. The most recent proposal from the Senate brings Russia into the fray, threatening to end WTO cooperation with any country found to be engaging in rather ill-defined "nuclear cooperation" with Iran. Like other similar measures in Congress, this one seems likely to pass-if in amended form. At the least, it threatens one of the few remaining areas of strong U.S.-Russian collaboration-civilian nuclear programs to purchase spent Russian nuclear fuel.

Back in the January/February issue of The National Interest, I wrote:

The United States is going to face a number of challenges and disappointments over the next two years-Iran, Iraq, North Korea, China and Russia, among others. The first reaction of many U.S. politicians is to be confrontational. Easing tensions with rogue states and with countries perceived to be opposing U.S. policies will not win the president points with those who prefer a muscular strategy. But decisions need to be made on the basis of long-term U.S. interests, not short-term sound bites.

Good advice to be following now.

Ian Bremmer, a contributing editor to The National Interest, is president of the Eurasia Group.