"The United States is simply responding to Iranian activities that have been going on for a while now that threaten not just to destabilize the chance for Iraq to proceed to stability but also that endanger our forces," Rice said before meeting with Israel's foreign minister.

Bush approved the strategy several months ago, U.S. officials said, in response to what Washington claims is Iran's support for terrorists inside Iraq and the alleged funneling of bombs to anti-U.S. insurgents.

Echoing other Bush administration figures, Rice said the U.S. does not intend to cross the Iraq-Iran border to attack Iranians.

Five Iranians were detained by U.S.-led forces after a raid Thursday on an Iranian government liaison office in northern Iraq. The move further frayed relations between the two countries.

The United States accuses Iran of helping provide roadside bombs that have killed American troops in Iraq. Also, a bitter standoff already exists over Iran's nuclear program.

Rice told reporters that the Iranian office was not a diplomatic consulate, which would be protected by international treaty.

The State Department said Friday that U.S.-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.

State Department spokesman Tom Casey said there was no truth to reports that Iran was carrying out legitimate diplomatic activity at the site.

But Iraqi Foreign Minister Hoshyar Zebari, a Kurd, contended 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 U.S. raid constituted an intervention in Iranian-Iraqi affairs