Troops from the Missouri National Guard prepared to deploy around Ferguson on Tuesday as the city awaits a grand jury's decision on whether to indict a white police officer who shot and killed an unarmed black teenager in August.
Governor Jay Nixon has declared a state of emergency in Missouri but said troops would play a backup role to police in response to any protests that develop after the decision.
People around St. Louis are braced for a possible new wave of protests similar to those that followed the Aug. 9 fatal shooting of 18-year-old Michael Brown, particularly if Ferguson police officer Darren Wilson is not charged.
Officials have said the grand jury's decision is likely to come this month.
Nixon on Tuesday was due to swear in the members of a new "Ferguson Commission," a group charged with reviewing the social and economic conditions that contributed to the unrest that followed Brown's death and coming up with suggestions for how to improve them.
More than one out of five residents of Ferguson, a predominantly black city of about 21,000 people, live below the poverty level, a rate that is above the state average, according to U.S. Census data.
Nixon declined to say how many National Guard troops would be assigned to the St. Louis area or where they would be stationed.
Peaceful demonstrations were held around St. Louis on Sunday and Monday and some local leaders expressed frustration over Nixon's state of emergency declaration.
"The National Guard is called in when policing has failed. Military presence in my city will mark a historic failure on the part of (government)," Antonio French, a St. Louis alderman, said on Twitter. "This is not a war. There is no military solution."
Police in Ferguson were criticized for taking a military posture in response to the August demonstrations, regularly deploying officers in riot gear and using tear gas and rubber bullets against crowds that torched two businesses in the St. Louis suburb and at times threw rocks and gasoline bombs at police.
Police in St. Louis County have since gone through conflict de-escalation training and activist leaders have also been training potential protesters in nonviolent techniques in recent days. County police will take the lead in handling any protests or civic disorder, supplanting the Ferguson Police Department, Nixon said.
St. Louis Mayor Francis Slay said his city's police force would respond to demonstrations in their normal uniforms unless conditions became violent and that National Guard troops would not play a primary role in responding.
Some area schools have told parents they will dismiss students early when the decision comes and many businesses near the stretch of downtown that saw the worst rioting after Brown's killing have boarded up their windows as a protective move.
There are conflicting accounts of what happened, with some witnesses saying Brown had his hands up in surrender when he was shot and others describing a scuffle between Brown and Wilson.
(Additional reporting by David Bailey in Minneapolis; Editing by Peter Cooney and Doina Chiacu)