Despite three decades of hostility, the U.S. and Iran have at least one thing in common: Both are heavily committed to supporting Iraq's Shiite government.
On Monday, that mutual interest led to a rare meeting of the U.S. and Iranian ambassadors, who gathered at Iraqi Prime Minister Nouri al-Maliki's office in Baghdad. The talks took place despite a fresh increase in tensions between the two nations.
In recent weeks Iran has detained five Iranian-Americans for questioning, accusing some of spying, even as reports surfaced of new CIA covert operations against Iran. The U.S. is holding five Iranians it seized earlier this year in Iraq.
Iran, the U.S. claims, is smuggling deadly explosives into Iraq that are being used against U.S. convoys. And the U.S. is calling for new sanctions against Iran to counter the progress it is making in the nuclear realm.
The U.S. has two aircraft carriers battle groups in the Persian Gulf. Last week they carried out maneuvers near Iran's coast.
Vali Nasr, an expert on Iran and Iraq at the Naval Post-Graduate School, says the two sides are engaged in a proxy war in Iraq and the wider region.
They are, he says, "supporting enemies of one another and arming enemies of one another with the view to subverting the position of one another."
Beyond the talks, Nasr says, "there is the reality of what's happening to U.S.-Iranian relationships on the other side. And it's very difficult to see how this low-level meeting in Iraq with a very limited agenda is going to change the direction of the broader confrontation that we're seeing between Iran and the U.S."
Expectations on both sides are extremely low. The Bush administration has been quite vocal in recent weeks, criticizing Iran for numerous transgressions, in Iraq and beyond.
In Iran, senior government officials have downplayed the likelihood that anything good will come of the Baghdad meeting. And both governments are divided about the value of even holding the meeting.
Vice President Cheney has been on the record for years opposing engagement with Iran. He has his counterparts on the Iranian side, such as Hossein Shariatmadari, the editor of Kayhan, Iran's most prominent conservative daily newspaper.
Negotiating with America is like shaking hands with Satan, Shariatmadari said in mid-May on Iranian television, because the Americans are only interested in negotiations for their own sake, not to solve the problems of the Iraqis. They are trying to intimidate the world of Islam and use Iran in the process, he said.
Yet the irony is that the U.S. and Iran are both heavily committed to supporting Prime Minister Nouri al-Maliki's fragile government.
So Washington and Tehran do share some common strategic interests, notes Abbas Milani, director of the Iran Democracy Project at Stanford University.
"They both want the Shiite government strengthened. They both want Maliki to survive, for different reasons," Milani says. "The U.S., because it sees it as the only hope. For Iran, because it's a dream come true. The U.S. is now spending money and military life and limb to strengthen a government that is very much a friendly force toward the regime."
But so many other issues get in the way of possible cooperation in Iraq.
One is the recent detention in Tehran of several Iranian-Americans, including Haleh Isfandiari, who is associated with the Woodrow Wilson Center for Scholars in Washington. That center is headed by Lee Hamilton, co-director of the Baker-Hamilton Iraq Study Group, which endorsed engagement with Iran.
President Bush noted the arrests at his news conference last week.
"We've made it very clear to the Iranian government that the detention of good decent American souls who are there to be beneficial citizens is not acceptable behavior," the president said.
President Bush also called for additional sanctions against Iran for its refusal to suspend the enrichment of uranium.
When the two sides do focus on Iraq, Vali Nasr sees little chance the U.S. will do anything more than chide Iran about its behavior there.
"Iran's interests in Iraq are not being recognized through these talks," Nasr says. "Iran is not being engaged as a partner in Iraq by the United States in the manner that the U.S. is willing to engage Saudi Arabia, Jordan, Kuwait, or Turkey in discussions about Iraq. The talks as far as the U.S. is concerned are limited to persuading Iran to stop participating in Iraqi politics."
There is one other crucial area where Iranian and American interests coincide in Iraq, says Abbas Milani.
"They both have an overlap of interests in trying to limit the influence of al-Qaida," he says. "Al-Qaida is as much the enemy of the Shiites as it is the enemy of the Christian West. They consider the Shiites as much of an infidel as they consider the Christian West infidels."
But the distrust on both sides is so deep, there appears to be little chance that either side was talking seriously about common interests during the meeting in Baghdad Monday.