Chicago Police formed a line outside President Barack Obama's national campaign headquarters Thursday to prevent protesters from entering the building.
Earlier this week, eight protesters were arrested for walking into 130 E. Randolph, marching around the lobby and taking an escalator further into the building. The protesters, associated with the Catholic Worker Movement, were arrested for criminal trespass to property.
Thursday demonstrators gathered under the name Code Pink with groups including Women for Peace, the World Can't Wait and Veterans for Peace saying they want an end to NATO violence, particularly drone attacks.
Protesters said they will then march to the Canadian, British and German consulates to deliver letters with their demands.
Earlier Thursday the group Iraq Veterans Against the War held a news conference discussing their Sunday march, during which they will return medals they received during the war and speak out about what they call a failed mission.
They're asking fellow servicemen to stand down during the summit.
"All we are asking is that these NATO representatives come and acknowledge us as human beings and accept our medals as we return them to these NATO generals," said Aaron Hughes of Iraq Veterans Against the War.
If the generals don't come out and accept them, protesters said they will create a memorial site and leave the medals at McCormick Place.