US President Barack Obama's nomination of Chuck Hagel for defense secretary has been blocked in the Senate, after a vote failed to garner the 60 votes needed to end debate on the matter.

The vote was 50 to 40, falling short of the 60-vote supermajority, Xinhua reported.

The Senate would reschedule another vote later in February.

Four Republicans – Susan Collins of Maine, Thad Cochran of Mississippi, Lisa Murkowski of Alaska and Mike Johanns of Nebraska – joined Democrats and Independents in support of the nomination.

Republicans have been calling for more time to consider the nomination, saying it was too early to clear Hagel's nomination.