The police killing of a second black St Louis-area man in 11 days has threatened to further enflame tensions.
On Tuesday, police officers shot dead a man who brandished a knife at them, St Louis Police Chief Sam Dotson said.
The 9 August police shooting of Michael Brown, 18, has sparked days of violent protests in the town of Ferguson, prompting a heavy police crackdown.
There is widespread anger against the mainly white police force for killing Mr Brown, who was unarmed.
Brown’s family say his funeral will take place on Monday.
US Attorney General Eric Holder is due to visit Ferguson on Wednesday to meet officials investigating the killing.
Tuesday’s police shooting has threatened to further inflame tensions within the community.
According to police, in the early afternoon, two officers shot and killed a knife-wielding man four miles (6.4km) from the site of Brown’s killing.
St Louis Police Chief Sam Dotson said witnesses reported the man had been behaving in an erratic manner, and emphasised the officers had a right to defend themselves.
“The suspect turned toward officers, pulled out knife in an overhand grip, told officers to ‘shoot me now, kill me now,’” he told reporters.
In another development in the Michael Brown case, the St Louis county prosecutor’s office on Tuesday said it would present evidence against the officer who killed Brown to a grand jury on Wednesday.
The citizen panel will determine whether or not to charge Darren Wilson with a crime.
Both St Louis officials and the US justice department are conducting investigations into the case, which has provoked demonstrations throughout the country.
Witnesses have said Brown was shot as he held his hands up in a position of surrender, while the police and supporters of Wilson have said he fired during a fight with Mr Brown.