WASHINGTON — The Bush administration is sending strong signals that U.S. troop reductions in Iraq will slow or stop altogether this summer, a move that would jeopardize hopes of relieving strain on the Army and Marine Corps.

The indications of a likely slowdown reflect concern by U.S. commanders that the improvement in security in Iraq since June — to a degree few had predicted when President Bush ordered five more Army brigades to Iraq a year ago — is tenuous and could be reversed if the extra troops come out too soon.

One of those extra brigades left in December and the other four are due to come out by July, leaving 15 brigades, or roughly 130,000 to 135,000 troops — the same number as before Bush sent the reinforcements.

The Army in particular wants additional reductions to enable it to shorten Iraq tours from 15 months to 12 months.

Gen. David Petraeus, the top U.S. commander in Iraq, is scheduled to report in April on possible additional cutbacks and any recommended changes in strategy. Petraeus recently said it would be prudent to “let things settle a bit” after the current round of troop cuts is completed in July before deciding whether and when to reduce further.

A senior administration official said Petraeus has made clear he is “concerned about a rush to 10” — a reference to the 10-brigade force level that some administration officials see as an attractive target to hit by the time Bush leaves the White House a year from now. The administration official said “it really is not determined” yet whether conditions in Iraq will permit further cutbacks. The official briefed reporters last week at the White House on condition of anonymity.

The first sign Bush might endorse a pause in troop reductions came earlier this month when he recounted for reporters his meeting with Petraeus in Kuwait on Jan. 12.

“My attitude is, if he (Petraeus) didn’t want to continue the drawdown, that’s fine with me, in order to make sure we succeed,” Bush said. “I said to the general, if you want to slow her down, fine; it’s up to you.”

In his State of the Union address Monday, Bush emphasized the risks of continuing the cutbacks beyond July.

“Any further drawdown of U.S. troops will be based on conditions in Iraq and the recommendations of our commanders,” Bush said. “General Petraeus has warned that too fast a drawdown could result in the ‘disintegration of the Iraqi security forces, al-Qaida-Iraq regaining lost ground, (and) a marked increase in violence.’ “

U.S. military death

The latest identification reported by the U.S. military of personnel killed in Iraq:

Army Maj. Alan G. Rogers, 40, Hampton, Fla., died Sunday of wounds suffered from an explosive in Baghdad; assigned to the Military Transition Team, 1st Brigade, 1st Infantry Division, Fort Riley, Kan.

Army Sgt. Mikeal W. Miller, 22, Albany, Ore.; died Sunday of wounds suffered in Baghdad when his vehicle struck an explosive; assigned to the 3rd Squadron, 61st Cavalry Regiment, 2nd Brigade Combat Team, 2nd Infantry Division, Fort Carson, Colo.