Secretary of State Condoleezza Rice says recent raids against Iranian operatives in Iraq are part of a broad military offensive against Iranian networks in the country authorized months ago by President Bush.
In an interview with The New York Times, Rice says the president made the decision after U.S. officials saw increasing activity among Iranians in Iraq, and "increasing lethality in what they were producing."
The newspaper says Rice is referring to evidence that Iran is responsible for producing the most sophisticated roadside bombs used against American troops in Iraq.
The United States accuses Iran of providing material support to insurgents, and of allowing terrorists to use Iranian territory to cross in and out of Iraq.
U.S. forces detained five Iranians Thursday in a raid on an Iranian government liaison office in the northern Iraqi city of Irbil.
U.S. officials say the Iranians were associated with attacks against U.S. and Iraqi forces.
Iran has condemned the U.S. raid and urged Iraq to secure the release of the detained Iranians.
Earlier Friday, aides to Iraqi President Jalal Talabani said he will travel to Syria Sunday for talks with Syrian President Bashar al-Assad. The two leaders are expected to discuss border security issues.
Iraq and Syria restored diplomatic ties last month after about 25 years.
The United States accuses Syria of allowing fighters to cross into Iraq to attack U.S.-led forces. Syrian officials deny the charge.
Some information for this report was provided by AFP.