BAGHDAD - Americans have opened nearly 1,000 new graves to bury US troops killed in Iraq since Memorial Day a year ago. The figure is telling - and expected to rise in coming months.

1st Sgt. Aldo Galeana, 42, from San Diego, Calif. of Delta Company, 4th Battalion, 31st Infantry Regiment adds Pfc. Joseph Anzack's photo to the company's shrine to fallen soldiers in Quarghuli village near Youssifiyah, 12 miles (20 kilometers) south of Baghdad, Iraq Saturday, May 26, 2007. [AP]

In the period from Memorial Day 2006 through Saturday, 980 soldiers and Marines died in Iraq, compared to 807 deaths in the previous year. And with the Baghdad security operation now 3 1/2 months old, even President Bush has predicted a difficult summer for US forces.

"It could be a bloody -- it could be a very difficult August," he said last week.

US commander Gen. David Petraeus on Saturday acknowledged the increase in casualties as a result of the American surge in forces to regain control of Baghdad.

"We're doing heavy fighting. This is a fight. There's a war on out there," he told reporters at al-Asad Airbase in western Iraq.

Michael O'Hanlon, a military analyst with the Brookings Institution and a consultant to the bipartisan Iraq Study Group, said the increased casualties were a result of the security operation.

Thousands more American soldiers are patrolling the streets and living in isolated outposts across Baghdad, leaving them more vulnerable to attack. He also said the increase in raids on extremist Shiite militiamen had brought a wave of retaliatory attacks.

"We're out there on the streets a lot more. There are more patrols going on every day, so we're more open to attacks," O'Hanlon said.

Stephen Biddle, a military expert at the Council on Foreign Relations and a member of a group that spent weeks in Iraq assessing the situation for Petraeus and US Ambassador Ryan Crocker, agreed that more American deaths were likely.

"The biggest change in their (insurgent and militia) tactics is that they've changed to exploit the vulnerabilities we've opened ourselves up to. They see a new, small American base in their neighborhood, three blocks away, and they're going to car bomb it," said Biddle.

"We're going to see a spike in the short term," said Biddle. "But the likelihood is that in six months we'll see a drop in casualties as these areas become more secure. The problem is, what about the rest of the country?"

By the end of Saturday at least 100 American troops had died in the first 26 days of May, an average of 3.85 deaths a day. At that pace, 119 troops will have died by the end of the month, the most since 137 soldiers were killed in November 2004, when US troops were fighting insurgents in Fallujah.

As of Saturday, May 26, 2007, at least 3,451 members of the US military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count. The figure includes seven military civilians. At least 2,817 died as a result of hostile action, according to the military.

Military announces 8 US deaths in Iraq