U.S. intelligence now discounts reports that the leader of al Qaeda in Iraq, Abu Musab Zarqawi, crossed into Syria earlier this year for a summit with the heads of Iraqi insurgent groups to map out a new strategy of suicide bombings against U.S. and Iraqi forces, administration officials said yesterday.

The intelligence assessment contradicts an assertion last month by a senior U.S. military official in Baghdad that Zarqawi had called the April summit in Syria. After a brief lull in violence following the January election, the pace of suicide bombings has picked up dramatically in Iraq.

U.S. officials now say U.S. intelligence was always skeptical of the military's assertions about Zarqawi, which they said were based largely on questionable information obtained during the interrogation of a detainee in Baghdad. Reports that Zarqawi made the trip to Syria further inflamed tensions between the Bush administration and the government of President Bashar Assad.

The behind-the-scenes split over Zarqawi's alleged meeting underscores a divergence of views within the administration on Syria's role in the Iraqi insurgency -- and whether it is actively fomenting the campaign against the U.S. military presence or playing a murkier and less direct role by looking the other way in the flow of personnel and funds.

"There's no question that Syrian territory plays a significant role with regard to how the outside figures into the insurgency in Iraq. The problems with the regime are a mixture of willingness and capability," said a senior intelligence official, who spoke on the condition of anonymity. "That mixture depends on what dimension of the problem you're looking at."

From the time of the original report, the CIA discounted reports of a Zarqawi trip, which would have symbolized a significantly heightened Syrian role in Iraq's violence, U.S. officials say. It did not match the pattern of movements by Zarqawi, a Jordanian-born extremist who has pledged loyalty to al Qaeda leader Osama bin Laden. It also did not match the pattern of Syrian complicity in the insurgency.

Washington has been turning up the heat on Damascus steadily in recent months. The United States suggested yesterday that Syria was linked to the car-bomb assassination of Samir Kassir, a prominent Lebanese journalist who had long called for Syria's withdrawal from Lebanon.

White House spokesman Scott McClellan said the United States had urged the United Nations to expand its investigation into the Feb. 14 car-bomb assassination of former Lebanese prime minister Rafiq Hariri to include the murder this week of Kassir.

"Over the years, Mr. Kassir was harassed by the Syrian and pro-Syrian Lebanese authorities . . . for fearlessly giving expression to the Lebanese aspirations for freedom," the U.S. Embassy in Beirut said in a statement. "His enemies were those who participated in Syria's occupation of Lebanon," which lasted from 1976 until the last troops were withdrawn in late April.

The United States also expressed concern about Syria's test firing this week of at least three Scud missiles, which initial reports indicate may have had components that could have helped disperse chemical weapons. The missiles had a range of 130 to 465 miles.

"The idea that Syria, which is already in the world's crosshairs regarding their failure to act on Hezbollah, Palestinian Islamic Jihad, terrorism, and Iraq's border, would then choose this moment to conduct these tests is ill-conceived and very disconcerting," a State Department official said, speaking on the condition of anonymity. "The timing -- with the Lebanese in the midst of a four-week electoral process -- makes it hard not to see the message they're sending: 'We're not weak and this is a capability we possess.' It's clearly an action intended to provoke."

A U.S. military official had said that Abu Musab Zarqawi met with Iraqi insurgents in Syria this year.