WASHINGTON — Senators agreed with only half of President Donald Trump’s military end-strength increase for fiscal 2019 in their first draft of the annual defense authorization bill, but would revamp the Pentagon’s personnel system to help better retain already serving troops.

Details of the plan were released late Thursday, a day after the Senate Armed Services Committee finished its closed-door deliberations on the $716 billion budget policy measure.

The spending totals largely echo both the White House’s and House’s spending requests for fiscal 2019, but differ in the specifics of how that money should be spent.

On the personnel side, the most striking difference is in the number of new troops to be added to the services next year. The White House had asked for an end strength of 15,600 troops across all four services, a plan that House lawmakers officially agreed to in a vote earlier on Thursday.

But the Senate committee’s plan — which still must be adopted by the full chamber in coming months — calls for an increase of only about 8,600 new service members.

The Army would see a boost of about 2,200 soldiers, as opposed to the 4,000-person increase in the White House plan. The Navy would see 3,000 more instead of the president’s 7,500-person request. The Air Force would get only 600 more airmen instead of the 4,000 the administration wants.

In all three plans, the Marine Corps will see a boost of only 100 troops.

In a statement, committee officials said the plan provides the Defense Department with “a strategic framework that establishes clear priorities and helps make tough choices.” It passed out of committee by a vote of 25-2.

Offsetting the smaller end-strength boosts are efforts to “modernize the 38-year-old officer personnel system to provide career flexibility and better serve the demands of today’s force,” with a goal of helping to better retain mid-career officers.

The bill includes alternative promotion schedules that “remove predetermined officer promotion timelines” for certain specialties in lieu of more flexible promotion and career continuation schedules.

Spot promotion authority would be extended for all ranks up to O-6. Officers in grades 0-2 or above would also be allowed to serve up to 40 years, but the measure also requires annual authorization of all mid-grade officers.

Committee officials did not provide specifics of the new personnel system rules, but are expected to release details in coming days.

Whether House lawmakers will go along with those plans — or the smaller end strength boosts — remains to be seen. The chamber overwhelmingly passed its $717 billion authorization bill version overwhelmingly on Thursday morning, and neither of those issues had been contentious in the committee or full chamber debate.

The Senate’s legislation does call for a 2.6 percent pay raise for troops starting in January, matching the request from the White House and the House authorization plan. That all but assures troops their largest pay raise since 2010, although the figure is only equal to the expected rise in private-sector wages.