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 take place 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 take place 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-Qaida-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.