Washington (AFP) – U.S. President Barack Obama promised Monday “limited” use of National Guard troops to quell unrest in a Missouri town after a white police officer shot dead an unarmed black teenager.

“I’ll be watching over the next several days to assess whether in fact, it’s helping rather than hindering progress in Ferguson,” Obama told reporters, as he pressed for calm from both sides, saying there was “no excuse” for excessive force by security forces and urging protesters to act peacefully.

AFP Photo/Michael B. Thomas