Major budget cuts initiated on Friday will endanger the US military’s ability to conduct its missions, Pentagon chief Chuck Hagel has warned. His comments came before President Barack Obama authorised cuts in domestic and defence spending, following the failure of efforts to clinch a deal with Republicans on cutting the deficit.

Hagel, whose budget at the Pentagon is set to be cut by about $46 billion, said earlier: “Let me make it clear that this uncertainty puts at risk our ability to effectively fulfill all of our missions.”

In contrast with his predecessor Leon Panetta, who branded the cuts a “doomsday mechanism” and “fiscal castration,” Hagel was more measured two days after taking office as defence secretary.

Officials say they will have to trim the working week of 800,000 civilian workers, scale back flight hours of warplanes and delay equipment maintenance.