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Washington - An order from US President Bush authorized a series of US raids against Iranians in Iraq as part of a broad military offensive, Secretary of State Condoleezza Rice said Friday.

Bush issued the order several months ago, Rice told The New York Times as she prepared to visit the Middle East. She said the president acted "after a period of time in which we saw increasing activity" among Iranians in Iraq "and increasing lethality in what they were producing."

Five Iranians were detained by US-led forces this week after a raid on an Iranian government liaison office in northern Iraq, a move that has frayed even further the relations between the two countries. The United States accuses Iran of helping provide roadside bombs that have killed American troops in Iraq, and a bitter standoff already exists over Tehran's nuclear program.

Rice, according to a story for the Saturday print editions of the Times, described the military effort against Iranians in Iraq as a defensive "force protection mission." Concerns that Iran was trying to further destabilize the country also motivated the raids, she told the newspaper.

"We think they are providing help to the militias as well, and maybe even the more violent element of these militias," she said.

The State Department said Friday that US-led forces entered an Iranian building in Kurdish-controlled Irbil because information linked it to Revolutionary Guards and other Iranian elements engaging in violent activities in Iraq. There was no truth to reports that Iran was carrying out legitimate diplomatic activity at the site, State Department spokesman Tom Casey said.

However, Iraqi Foreign Minister Hoshyar Zebari, a Kurd, contended that the Iranians were working in a liaison office that had government approval and was in the process of being approved as a consulate. In Iran, Foreign Minister Manouchehr Mottaki said the US raid constituted an intervention in Iranian-Iraqi affairs.

On Friday, US officials said there was no immediate plan to strike targets in Iran, but they also wouldn't rule out military action. Their comments came after Bush vowed in a prime-time address to the nation to go after Iranian terrorist networks feeding the insurgency in Iraq.

Bush's remarks Wednesday in a speech announcing his plan to boost US forces in Iraq prompted questions from members of Congress about whether the US is considering attacks on Iranian territory. Administration officials have long refused to rule out any options against Iran but said military action would be a last resort.

US Defense Secretary Robert Gates and Gen. Peter Pace, chairman of the Joint Chiefs of Staff, on Friday told the Senate Armed Services Committee that while US forces are trying to prevent Iran and Syria from disrupting US forces in Iraq, there were no immediate plans for an attack.

US Secretary of Defense Robert Gates (L) listens during the Senate Armed Services Committee hearing about Iraq on Capitol Hill in Washington January 12, 2007. Next to Gates is Chairman of the Joint Chiefs Gen. Peter Pace. [Reuters]

"We believe that we can interrupt these networks that are providing support through actions inside the territory of Iraq, that there is no need to attack targets in Iran itself," Gates told the panel, adding that he continues to believe that "any kind of military action inside Iran itself, that would be a very last resort."

Pace said special operations forces are continually battling insurgents who are getting aid from Iran.

"I think one of the reasons you keep hearing about Iran is because we keep finding their stuff in Iraq," Pace said.

Sen. Joseph Biden, D-Del., chairman of the Foreign Relations Committee, wrote to Bush on Thursday asking for clarifications on the administration's stance toward attacking Iran. Sens. John Warner, R-Va., and Robert Byrd, D-W.Va., raised the issue at a hearing Friday.

"The president seems to have placed diplomacy on the back-burner again," Byrd said.

In his speech Wednesday, Bush chastised Iran and Syria for not blocking terrorists at their borders with Iraq. He specifically blamed Iran for providing material support for attacks on American troops.

"We will disrupt the attacks on our forces," Bush said. "We will interrupt the flow of support from Iran and Syria. And we will seek out and destroy the networks providing advanced weaponry and training to our enemies in Iraq."

On Friday, White House spokesman Tony Snow called the suggestion that war plans were under way an "urban legend."

"What the president was talking about is defending American forces within Iraq, and also doing what we can to disrupt networks that might be trying to convey weapons or fighters into battle theaters within Iraq to kill Americans and Iraqis," Snow said.