Iraqi Prime Minister Nouri al-Maliki has been quoted saying that US troops should leave Iraq "as soon as possible".

He called US presidential candidate Barack Obama 's suggestion of 16 months "the right timeframe for a withdrawal".

In an interview with Germany's Der Spiegel weekly, Maliki said he was not seeking to endorse the Democratic US presidential contender, but that keeping troops in Iraq for too long would cause trouble.

Obama has pledged to withdraw combat troops from Iraq within 16 months if he is elected.

"That, we think, would be the right timeframe for a withdrawal, with the possibility of slight changes," Maliki was quoted as saying.

"Those who operate on the premise of short time periods in Iraq today are being more realistic. Artificially prolonging the tenure of US troops in Iraq would cause problems."

Asked when US forces would leave Iraq , he responded: "As soon as possible, as far a we're concerned".

Obama arrived on his first visit to Afghanistan on Saturday, less than four months before the general election. Obama also is expected to stop later in Iraq .

Obama's Republican presidential rival, John McCain , has criticised him for his lack of experience in the region. McCain has suggested he would pursue an Iraq strategy "that's working" - a reference to the troop buildup credited for sharply reducing violence in the country.

Maliki is scheduled to visit Germany next week for talks with Chancellor Angela Merkel and business leaders amid a renewed German push in helping to rebuild Iraq .

Berlin had opposed the 2003 US-led invasion of Iraq .