UPDATE 2-Gates due to unveil defense budget soon-Air Force

* Most senior meetings on budget done

* Gates in final deliberations

* 55 major program changes

(Adds analyst quote, byline)

By Andrea Shalal-Esa

COLORADO SPRINGS, Colorado, April 2 (Reuters) - U.S. Defense Secretary Robert Gates is putting the final touches on the fiscal 2010 defense budget and will announce his decisions soon, Air Force Secretary Michael Donley said on Thursday.

"Most of our senior level meetings in the department are complete at this point," Donley told reporters at the Space Foundation's National Space Symposium.

"The secretary is in the final stages of his deliberations and I think you'll hear from him pretty soon on that subject," Donley said when asked about progress on the Pentagon's budget for fiscal 2010, which begins Oct. 1.

Donley gave no details, but one defense analyst with close ties to military officials said the budget included major changes to 55 weapons programs, including some program cancellations and a few increases in funding.

U.S. defense companies have been anxiously awaiting news about major weapons programs and concerns about pending cuts have weighed heavily on defense stocks in recent weeks.

President Barack Obama asked Congress in February to increase the Pentagon's regular budget to $533.7 billion next year -- up 4 percent, or $20.4 billion, from its spending plan for the current year, drawn up under the Bush administration.

Defense officials have been working out the details for exact funding levels within the overall budget, which brings the curtain down on the big growth in defense spending under the Bush administration but still gives the Pentagon an increase at a time of economic crisis.

In February, Gates said the Pentagon fared better than had been feared, but said the military faced "hard choices" about specific weapons programs, especially those that have faced cost overruns or management problems in recent years.

Defense analyst Loren Thompson said he had learned that Gates planned to brief top lawmakers about the budget over the weekend, followed by a news conference next week, possibly as early as Monday.

The budget included major changes -- either increases or decreases -- to 55 major weapons programs, said Thompson, chief operating officer of the Virginia-based Lexington Institute.

He said programs that would be cut included a ground-based missile defense program run by Boeing Co (BA.N), a big Army modernization program also led by Boeing, and a new Navy destroyer built by Northrop Grumman Corp (NOC.N) and General Dynamics Corp (GD.N), as expected.