WASHINGTON (Reuters) - President Barack Obama's budget would slash less from the Pentagon than automatic "sequester" spending cuts which have started to kick in, but would still eliminate $150 billion from projected defense spending over a decade, a U.S. official told Reuters on Wednesday.

The official, speaking on condition of anonymity, said $34 billion in cuts would take place during the first five years of the plan.

"That's what we really have to plan for in the near term. So there is that kind of certainty," the official said. "This would require of course de-triggering sequestration, then that's certainty that would be welcome."

The remaining cuts would "backloaded" into the last five years. The cuts come on top of $487 billion in defense spending cuts approved in 2011.

(Reporting by Phil Stewart)