Martin Dempsey assumed on Friday the role of top US commander overseeing both the Iraq and Afghanistan security, replacing William J Fallon as the head of the US Central Command.
Although it is unclear whether the new assignment is temporary or permanent, Dempsey will be in the position for some time, according to news reports.
Fallon resigned on Tuesday amid media reports that he was at odds with the White House over Iran. Dempsey used to be his deputy.
US President George W Bush is not expected to nominate a permanent successor to Fallon until David Petraeus, top US commander in Iraq, submits reports on Iraq to Congress April 8-9.
It looks very likely that Dempsey could stay in the new post, but other candidates, including Petraeus, are also in the fray. Born in 1952, Dempsey's military career spans over three decades.
He was the commander of the first armoured division in the early stages of the Iraq war and was promoted to Central Command deputy commander last year.