BAGHDAD – In a historic step for two of the world’s bitterest foes, the U.S. and Iran are to open a direct dialogue on issues relating to Iraq at talks to be held in Baghdad, the two countries said Sunday.

The talks will focus strictly on the problems confronting Iraq, not on the range of disputes plaguing the U.S.-Iranian relationship, including Iran’s nuclear program, the White House said, limiting expectations for the meeting.

The dialogue, to be held at the ambassador level, nonetheless will mark a rare instance of direct contact between Iran and the U.S., which severed diplomatic relations in 1980 and have communicated only sporadically since.

The announcement came on one of the bloodiest days in Iraq in weeks, with at least 126 Iraqis reported killed in bombings and shootings. Thousands of U.S. troops spent the day scouring farmland south of Baghdad for three U.S. soldiers feared captured by Al Qaeda-affiliated insurgents in an ambush Saturday.

Under growing pressure to produce results in the Iraq war or bring the troops home, the Bush administration has been signaling for weeks that it is eager to open negotiations with Iran on Iraq’s future, an acknowledgment of the vast influence Iran now wields in Iraq.

Iran had been holding out, however, seeking guarantees that its nuclear program won’t be on the table and pressing for the return of five of its citizens detained in January in Irbil by U.S. forces.

In a turnabout Sunday, Iran’s Foreign Ministry announced it had agreed to the request for talks, and Vice President Dick Cheney, on a tour of Arab countries aimed at shoring up support for the Iraqi government, confirmed that the U.S. would participate. The White House said Ryan Crocker, the U.S. ambassador to Iraq, would represent America.

Both sides cited their concern for Iraq and its stability as their sole reason for agreeing to launch a formal channel of communication that would have been unthinkable throughout most of the Islamic Republic of Iran’s 28-year existence.

“The president authorized this channel because we must take every step possible to stabilize Iraq and reduce the risk to our troops even as our military continue to act against hostile Iranian-backed activity in Iraq,” White House spokesman Gordon Johndroe told reporters traveling with President Bush in Virginia.

“Iran has agreed to talk to the U.S. side over Iraq, in Iraq, in order to relieve the pain of the Iraqi people, to support the government and to reinforce security in Iraq,” Iranian Foreign Ministry spokesman Mohammed Ali Hosseini was quoted as saying by the Iranian news agency.

The agency said a date for the talks would be announced this week.

Iraq’s government, which has close ties to both countries and has been trying to mediate a dialogue between them, welcomed the news as a positive step toward stabilizing Iraq.

“Good relations between Iran and the U.S. will improve the situation in Iraq because it means Iraq will no longer be the battlefield for the two sides to use Iraqi soil to solve their differences,” said government spokesman Ali al-Dabbagh. “It will be good for the U.S., good for Iran and good for the region.”

Decades of mistrust

Iraqi officials see some form of U.S. accommodation with Iran as essential if the U.S. is to be able to withdraw its troops without triggering a bloodbath between the country’s Iranian-backed Shiite militias and the Sunni insurgency that is fighting the U.S. military occupation and the Shiite-led government.

Decades of mistrust are unlikely to be overcome quickly, however, and several past attempts to bring Iranian and U.S. officials together over Iraq have sputtered. Hopes that U.S. Secretary of State Condoleezza Rice would hold talks with her Iranian counterpart on the sidelines of a gathering of Iraq’s neighbors in Egypt early this month did not materialize, though a lower-level encounter did take place, marking the first time U.S. and Iranian officials are known to have met directly since President Bush designated Iran a member of “the axis of evil” in 2002.

The talks may backfire if Iraq’s Sunnis and the region’s Arab states perceive that the U.S. is conceding Iraq to Iran’s sphere of influence, said Mustafa al-Ani of the Dubai based Gulf Research Center.

“These countries supported Saddam Hussein during the Iran-Iraq war to prevent Iranian control of Iraq, and I don’t think their attitude is going to change,” said al-Ani. “It’s going to be civil war, and not just an Iraqi civil war – a regional civil war.”

America’s Arab allies are already deeply skeptical about the level of Iranian influence over Iraq’s Shiite-led government, and one of the chief goals of Cheney’s tour of the region is to persuade Arab states to be more supportive of the Iraqi government on which the U.S. is pinning its hopes for an exit strategy.

U.S. casualties have been mounting as the insurgency proves itself as resilient as ever. In a statement posted on its Web site, the Al Qaeda-affiliated Islamic State of Iraq said it was holding the three soldiers who went missing in Saturday’s ambush near the town of Mahmoudiyah, an attack in which four other U.S. soldiers and their Iraqi interpreter were killed.

Though the claim was not backed up by any evidence, the area in which the soldiers went missing is a known Al Qaeda stronghold and U.S. officials say it is plausible that Al Qaeda was responsible for the attack.

Two more U.S. soldiers were killed Sunday in separate attacks in Salahuddin and Anbar provinces, the U.S. military said, bringing to 42 the number of casualties in May.

U.S. commanders blame at least some of the recent increase in casualties on the supply to insurgents of sophisticated roadside bombs, known as explosively formed penetrators, that U.S. officials say could only be coming from Iran.

The question of Iran’s support for the insurgency – including, U.S. officials say, the Sunni insurgency – will be high on the U.S. agenda for the talks.

Iran, deeply concerned that U.S. troops in Iraq could be used to wage war against Iran, will be looking for guarantees that the troops will go home, Iraqi officials say.