The shipments include weapons and explosives sent by vehicles that were detected during the past several months going to several training camps inside Syria, which has become a key backer of anticoalition forces in Iraq, according to defense officials familiar with reports of the shipments.
One defense official said the pipeline was uncovered as part of efforts to discover what happened to Iraq's arms programs — conventional as well as weapons of mass destruction.
"Everyone seems to have forgotten that there was the prospect of ongoing traffic in munitions ... that could then be re-imported into Iraq with quite considerable effect," the official said. "We are pursuing the extent and location of that."
The weapons are traveling by covered trucks and unmarked vans along routes that appear to have been set up before the U.S.-led military invasion of Iraq last year.
The night-time deliveries are reported to include small arms, bombs and explosives pilfered from some of the several thousand weapons depots scattered throughout Iraq. The Pentagon has identified more than 8,700 weapons dumps and is continuing to find caches almost daily, officials said.
The arms and explosives come back into Iraq with the Syrian-based insurgents and terrorists, the officials said.
Camps were set up by former officials in the Saddam Hussein regime and are being used to train foreign fighters who are continuing to flow into Iraq to conduct attacks on U.S. and allied forces, the official said.
Homemade bombs fashioned from artillery shells and other military ordnance stored in Iraq have caused hundreds of casualties among coalition forces.
The Syrian border with Iraq is under intense surveillance by U.S. intelligence agencies and patrols involving U.S. and allied military forces. Electronic surveillance includes unmanned aerial vehicles and satellite reconnaissance.
The weapons smuggling, however, appears to be done by Iraqis and others who have found ways to avoid the surveillance.
Some defense and intelligence officials said goods related to Saddam's chemical, biological and nuclear programs were sent covertly to Syria before the war.
Several thousand foreign fighters have infiltrated from Syria into Iraq, according to military officials who disclosed the flow to The Times last month.
The 600-mile desert border between Syria and Iraq has been a key smuggling route for decades, and the regime of Syrian President Bashar Assad has facilitated the foreign fighters' movement, providing travel papers and weapons in some cases.
Defense Secretary Donald H. Rumsfeld said last week that Syria and Iran "have been unhelpful to what it is we're trying to do in Iraq."
Mr. Rumsfeld said Syria's "dictatorship" opposes the development of a free political system in Iraq.
Mr. Rumsfeld said the border is easily crossed "and people, terrorists, have come across that border."
"Syria has been recalcitrant with respect to freeing up Iraqi assets that were frozen in their country, and large portions of it have been disappearing," Mr. Rumsfeld said.
Mr. Rumsfeld said recent sanctions imposed on Syria are an attempt to pressure its government to change its behavior.
He said he thinks that "it is ... appropriate that Syria not be rewarded."
"The hope is that through discussion, and debate, and consideration, diplomacy, that Syria will recalibrate its direction," he said after a speech at the Heritage Foundation.
"Whether that will happen, I don't know. I wish I did know. But in the meantime, we've got to make sure that they do as little damage to what we're trying to accomplish in Iraq as possible."
On May 11, the Bush administration announced new sanctions against Syria, noting Damascus' support for terrorists and its failure to keep anticoalition fighters from crossing into Iraq.
The sanctions bar U.S. exports to Syria and restrict Syrian assets held in the United States. They were imposed after Damascus failed to address U.S. concerns about support for terrorists and about Syria's arms programs.
President Bush said in announcing the sanctions that Syria's government "must understand that its conduct alone will determine the duration of the sanctions."
Mr. Bush also noted that insurgents "bent on sowing terror continue to cross into Iraq from Syria."
The export ban is expected to keep about $100 million in goods from going to Syria.
Signed into law in December, the sanctions were imposed under the 2003 Syria Accountability and Lebanese Sovereignty Restoration Act. The act called on Syria to close borders to military and equipment and anti-U.S. militants headed to Iraq.  http://www.2la.org/syria/iraq-wmd.php