By SHERYL GAY STOLBERG
Published: May 23, 2007

NEW LONDON, Conn., May 23 — President Bush, addressing head-on the criticism that Iraq has turned into another Vietnam, argued today that withdrawing from Iraq would be dangerous because, unlike the enemy in Vietnam, terrorists in Iraq have the capability and desire to strike Americans at home.

President Bush spoke at the U.S. Coast Guard Academy commencement ceremony on Wednesday. In a commencement speech at the Coast Guard Academy here, Mr. Bush also described what the White House called previously classified intelligence to build his case that Osama bin Laden is trying to turn Iraq into a “terrorist sanctuary” from which Al Qaeda can plot against the United States.

Even in trying to contrast the two wars, invoking the Vietnam analogy was unusual for Mr. Bush. It is a comparison he typically addresses only in response to questions.

“Now, many critics compare the battle in Iraq to the situation we faced in Vietnam,” Mr. Bush said. “There are many differences between those two conflicts, but one stands out above all: The enemy in Vietnam had neither the intent nor the capability to strike our homeland. The enemy in Iraq does.”

The comments brought immediate criticism from Democrats and some counterterrorism experts, who assaulted Mr. Bush for not acknowledging that the war itself helped open the door for terrorists to set up shop in Iraq.

“One day Bush tells us we are fighting in Iraq so that terrorists won’t come here, then he releases intelligence that says terrorists trained in Iraq are coming here. Which is it?” said Richard A. Clarke, a former national security adviser to three presidents, including Mr. Bush, in a statement released by the National Security Network advocacy group.

Mr. Bush has long argued that withdrawing from Iraq would create a vacuum that would allow Al Qaeda to flourish, and he reiterated that argument today, just as the White House is trying to wrap up negotiations on an Iraq spending bill. With Democrats pressing him to change course, he said, “We are at a pivotal moment in this battle.”

He painted a picture of a deepening terrorist menace even as he argued that Al Qaeda has been repeatedly thwarted by the United States and its allies.

In 2005, Mr. Bush said, Mr. bin Laden personally directed Abu Musab al-Zarqawi, a Jordanian terrorist who led the group Al Qaeda in Mesopotamia until his death last year at the hands of American forces, to develop a new terror cell that would plot attacks against the United States and other countries.

“Bin Laden emphasized that America should be Zarqawi’s No. 1 priority in terms of foreign attacks,” he said. “Zarqawi welcomed this direction. He claimed that he had already come up with some good proposals.”

The speech, given to 228 graduates under sunny skies overlooking the Thames River here, was a far cry from the president’s last Coast Guard Academy commencement address. That speech, delivered in May 2003, came just a few weeks after Mr. Bush declared an end to major combat operations in Iraq, and the president used it to sound a theme of victory. “In Iraq, America’s military and our allies carried out every mission, and exceeded every expectation,” Mr. Bush said then.

Today’s speech, by contrast, amounted to a defense of Mr. Bush’s policies, and Democrats and some national security experts accused the president of selectively releasing intelligence. Some argued that the speech, rather than build up Mr. Bush’s case for the war, undermined it by confirming that Iraq is already a haven for terrorists.

“The president today made the best case yet for why Congress must insist on a change of strategy in Iraq,” said Senator Harry Reid of Nevada, the Democratic leader. “Intelligence analysts concluded long ago that Iraq has indeed become a training ground and recruiting poster for a new generation of terrorists.”

Thomas Sanderson, a terrorism specialist at the nonpartisan Center for Strategic and International Studies, called Mr. Bush’s argument “completely ridiculous” and said Iraq would not have become a training ground for Al Qaeda had the United States not invaded. “We created the biggest terrorism training ground known, which is Iraq,” he said.

The assertion that Mr. bin Laden is thought to be communicating with insurgents in Iraq is not a new one. But Mr. Bush sought to infuse the information with previously unreleased details.

He said, for instance, that intelligence officials believe Mr. bin Laden had asked another top terror operative, Hamza Rabia, to help Mr. Zarqawi develop his terrorist cell by providing him with a briefing about Al Qaeda’s “external operations,” including information on attacks planned on American soil.

Mr. Bush said another senior Qaeda leader, Abu Faraj al-Libi, at one point suggested that Mr. bin Laden send Mr. Rabia himself to Iraq, with the idea that “Al Qaeda might one day prepare the majority of its external operations from Iraq.”

And the president said that Mr. bin Laden did try to send another Qaeda operative, Abd al Hadi al-Iraqi, to Iraq. But Mr. Hadi never made it, Mr. Bush said; he was captured and is now in detention at Guantánamo Bay, Cuba.