"It is wrong. Innocent people die," she said.
Police arrested at least eight people at the end of the march after the group laid mock coffins at a fence outside the White House.
Police said the protesters had defied orders to clear the pavement in front of the White House, and said they faced charges of failure to obey a lawful order.
The exact number of protesters was unclear but the rally drew a smaller crowd than the tens of thousands who marched against the war in 2006 and 2007under the administration of George Bush, the former US president.
"Obama policies in Iraq and Afghanistan are as criminal as Bush's," Mathhis Chiroux, a member of a group called the Iraqi Veterans Against the War, said, referring to Barack Obama, the US president.
"The US machine produces war regardless of who is president. We are killing innocents," the AFP news agency quoted him as saying.
Demonstrations were also held in the US states of New York and California among other places on Saturday.
Despite the protests, some analysts criticised the US mediafor failing to highlight awareness of the seventh anniversary of the start of the Iraq war.