WASHINGTON (AP)

The Senate yesterday confirmed President Barack Obama's choice to run the Pentagon, handing Ash Carter the unenviable task of steering the military, as the United States confronts Islamic State militants, conflict in Ukraine and other worldwide threats.

The vote in the republican-controlled Senate was 93-5. Carter will replace Chuck Hagel, the former Republican senator who had a rough relationship with Obama's insular group of national security advisers.

Carter will be Obama's fourth defence secretary in six years, joining a line of succession that began with Robert Gates and included Leon Panetta and Hagel.

One of Carter's first tasks will be helping to win support for Obama's call to Congress for new authority to use force against the IS extremists. Republicans and Democrats have reacted negatively to Obama's draft proposal, criticising both its limitations and vagueness.

In endorsing the 60-year-old Carter, Republicans expressed little hope that he would have better success in jelling with Obama's inner circle than Hagel did. The Vietnam War veteran was often the outsider and he announced in November he was stepping down.

The president's relationship with the Pentagon has often been strained.

Senate majority leader, Mitch McConnell, a Republican who backed Carter, said he "needs to have the courage to speak truth to power - to Congress, yes, but also to his commander in chief".

While moving ahead on Carter, Senate Republicans delayed a committee vote on Loretta Lynch, Obama's nominee for attorney general. Lawmakers said they had more questions for Lynch, the US attorney for the eastern district of New York who would become the nation's first black female attorney general if confirmed.

Democrats complained that Lynch is being held to a double standard compared to other nominees and said her nomination should be approved immediately. Her confirmation is expected after Congress' one-week recess.