DENVER -- Instead of the 5,000, 10,000, even 25,000 protesters organizers hoped for, only about 2,000 people actually marched through the streets of Denver -- even after a concert by the politically-charged band Rage Against the Machine.

Video: Protesters Arrested | Slideshow Of Protests

Authorities had prepared for thousands and thousands of protesters. Denver police called in a uniformed force of about 1,000 additional officers from around the metro area and even horse patrols from out of state. The federal presence has been nothing short of overwhelming.

Still, protesters kept the police busy.

A column of people three blocks long, led by members of the Iraq Veterans Against the War, marched from a Rage Against the Machine Concert at the Denver Coliseum to the Pepsi Center, where the Democratic National Convention was being held.

They were stopped just outside the "Freedom Cage" -- a fenced-in area just outside the Pepsi Center where police had designated as a safe protest zone, reported KMGH-TV in Denver.

"We are the veterans! The Iraq War veterans! The anti-war veterans!" they chanted along the 4-mile trek. "We are soldiers! Anti-war soldiers!"

The veterans, some in uniform, began the march in formation, chanting "She Wore a Yellow Ribbon," a marching song.

The veterans group said it wanted Democratic presidential candidate Barack Obama to agree to an immediate withdrawal of troops from Iraq. They also want full health care benefits for returning troops and veterans, and reparations to the Iraqi people for damage caused by the war.

The group sent a letter to Obama on Monday, and pledged to conduct a sit-in at the convention site until their message is heard.

Tensions mounted as police officers in riot gear pushed the group to contain themselves behind the fence.

Negotiations continued until, just before 8 p.m., when Marine Corps staff Sgt Jeff Key said that he and another member of the Iraq Veterans Against the War will meet with an Obama staffer to make sure their message is heard. The two were escorted by police to a meeting.

Key said the meeting lasted about 10 minutes. The Obama campaign confirmed the meeting but would provide no details, and Carter did not immediately return a call seeking comment.

Denver residents looked on from nearby.

"It was scary at first, but they're just marching. They're trying to be Americans, I guess," said Sylvester Williams, a Navy veteran from the Vietnam War. "I was part of Vietnam and that was a hoax. This Iraq (expletive) is even worse."

Jack Scott watched the marchers quietly.

"It's pretty neat, we can still do this in this country," he said.

Earlier in the day about 9,000 people attended a free concert at the coliseum, where a reunited Rage Against the Machine performed.

Jonny 5, Brer Rabbit and Andy Guerrero of the Denver group Flobots were with the marchers, as was Raymond "Boots" Riley of political hip-hop group The Coup, who also performed at the concert.

Protesters took special aim at the Fox News Channel.

In at least two instances this week, Fox News -- which is often accused of conservative leanings despite its "Fair and Balanced" claim -- was under siege by DNC protesters.

On Sunday, Fox reporter Griff Jenkins was doing a live shot of what he described as a 1,000-person antiwar protest march, when things went awry.

In the shot, which is still getting heavy play on YouTube.com, Jenkins attempts to ask some of the marchers what they were protesting. He did get one response not tainted with profanities -- "Stop the torture, stop the war" -- among a few others with F-words.

Jenkins and his photographer were then surrounded with protesters chanting in unison, "F--- Fox News."

Several of the F-word chants made it on the live air before an anchor resumed coverage at Fox News' studios.

Authorities said there have been about 135 arrests related to the convention over three days.

One protest group is taking issue with the law enforcement. Saying any trust had been lost with police, organizers of the protest group Recreate 68 announced plans Tuesday to sue the City of Denver.

Mark Cohn, a co-founder of the group, said they are talking to attorneys about a lawsuit.

"The promise at the beginning of all of this was, 'We stay peaceful, they stay peaceful,'" said Glenn Spagnuolo, also a founder of the protest group. "That truce was violated."

Denver police said it made limited use of pepper spray paintball-type bullets when the crowd, estimated at 300 people, refused requests to disperse.

Denver Police Lt. Ron Saunier defended the actions of police.

"Through the indications of a lot of things, we felt (the protesters) were getting ready to move down, start creating destruction of private property and possibly assaulting people," Saunier said.

Eighty-five people were arrested on charges of obstruction, disobeying lawful orders, and interfering with a police officer, Saunier said.