The governor of the US state of Missouri has declared a state of emergency and activated the National Guard ahead of a grand jury decision in the case of a black teenager shot and killed by a white police officer.
"As part of our ongoing efforts to plan and be prepared for any contingency, it is necessary to have these resources in place in advance of any announcement of the grand jury's decision," Governor Jay Nixon said in a statement.
The order also puts the St Louis County Police Department, rather than police in Ferguson, Missouri, in charge of policing protests.
Residents of Ferguson, which saw weeks of sometimes violent protests following the 9 August shooting death of 18-year-oldMichael Brown, are braced for the possibility of more unrest, particularly if the grand jury decides not to criminally charge Ferguson police officer Darren Wilson.
The past two days have seen protests around the area in anticipation of the grand jury's report.
Several dozen demonstrators took to the streets in Clayton, Missouri, where a grand jury is meeting.
"We want an indictment. The cops don't like it," the protesters chanted as they marched in freezing temperatures.
Some area schools have told parents they will dismisss students early when the decision comes and many businesses near the stretch of downtown that saw the worst rioting after Mr Brown's killing have boarded up their windows as a protective move.
Officials have said the grand jury's decision is likely to come this month.
The Missouri National Guard will have a background role in the city of St Louis when they are deployed to support police in anticipation of the decision, St Louis Mayor Francis Slay said.
"This would be from our standpoint a secondary role," Mr Slay told a news conference. "We would not have the guard on the front lines interacting with, dealing with, confronting protesters."
Mr Slay said they did not yet know how many National Guard troops would be sent to St Louis or exactly when, but believed they could be sent some time this week.
Video and audio published over the weekend by the St Louis Post-Dispatch showed Officer Wilson leaving the police station and returning to it hours after the shooting.
There are conflicting accounts of what happened, with some witnesses saying Mr Brown had his hands up in surrender when he was shot and others describing a physical altercation between the police officer and the teenager.
Many protesters expressed anger at word over the weekend that Officer Wilson may be able to return to his job if he is not indicted, although local police said he would be fired immediately if charges are brought.
Protest organisers planned to demonstrate at the Ferguson Police Department when the grand jury's decision comes back, and later at the county courthouse in Clayton.
Ferguson Mayor James Knowles expressed confidence today in the city's police department and its chief, Thomas Jackson.
"Right now, what we need is continuity in the police department and the chief has made tremendous relationships with a number of protesters and so I think that's what those protesters want," Mr Knowles said.
"The conversations we have been able to have with people have been very productive. ... We need to have a mutual understanding before we can move forward."
