Although participation is shrinking, anti-war protestors still marked the six anniversary of the start of the Iraq war across the country on Thursday.

A group of war veterans made a modest protest near the White House in the morning.

Known as "Iraq Veterans Against the War," the group said it would hold a three-day vigil outside the White House to call for ending "occupations in Iraq and Afghanistan."

US anti-war demonstrators stage a protest in New York, the United States, March 19, 2009, marking the 6th anniversary of the start of Iraq war. [Xinhua]

Adam Kokesh, who served in Iraq, was critical of President Barack Obama's Iraq and Afghanistan policies.

"Relabeling the remaining forces in Iraq 'noncombat troops' will not change the fact that these occupations are being perpetuated to maintain a criminal empire," he said.

Obama is known for his long opposition to the war but recently he has frustrated some of his anti-war supporters for his failure to stick to a campaign promise to withdraw all US combat troops within 16 months after taking office.

In announcing his war plan last month, the president opted for a 18-month timetable to moderate military commanders' resistance to a quick withdrawal from Iraq.

His decision to keep a large presence of 50,000 "non-combat" forces after August next year didn't please many Democrats either.

"The backlash of the actions by both administrations, of pursuing the enemy outside of the combat regions will only spread the violence further," said James Gilligan, who served in both Iraq and Afghanistan.

The veterans also don't think Obama's policy to shift the war focus to Afghanistan was a good choice.

"No matter how Obama spins a surge into Afghanistan, it's still a criminal occupation and we don't want it," said Bryan Casler, another veteran.

In San Francisco, police handcuffed several war protesters who blocked a downtown intersection in the afternoon.

Several dozen protesters had gathered at the intersection and dozens more onlookers had stopped to watch.