President Bush is expected to announce next week that Army tours in Iraq and Afghanistan will be reduced from 15 to 12 months, FOX News has confirmed.

A senior U.S. official told FOX News Friday that Bush will make the announcement April 10 after Gen. David Petraeus and Ryan Crocker, U.S. ambassador to Iraq, testify on Capitol Hill.

The shorter tours are unlikely to go into effect until after July, when the final surge brigades are withdrawn.

The Associated Press reported Friday that the decision is expected to get final, formal approval in the days ahead, and it comes as Petraeus, the top U.S. commander in Iraq, prepares to deliver a progress report to Congress next week on the improved security situation there. He is also expected to make recommendations for future troop levels.

A senior administration official told the Associated Press that plans are to deploy soldiers for 12 months, then give them 12 months rest time at home. Exactly which units would be affected is not yet clear. The official spoke on condition of anonymity ahead of the announcement.

Officials have been publicly tightlipped in recent days about the move to reduce the tours.

Defense Secretary Robert Gates told reporters on his plane earlier Friday that "there will be a decision (on the tour reduction) fairly soon."

He said Petraeus' testimony would be a "big piece" of what the administration proposes. But he also cautioned that cutting troops' time on the battlefront will impose limits on what the military can do in the future.

Gates spokesman Geoff Morrell stressed that nothing's official until after the Petraeus testimony.

"Everyone from Secretary Gates and Army Chief of Staff Casey on down is working hard to figure out when and how to reduce tour lengths for soldiers in Iraq and Afghanistan. Both of them have said it will be possible to drop from 15 to 12 month tours once we reduce to 15 brigade combat teams in Iraq," he said. "If conditions on the ground permit, that should happen by the end of July. However, though it may soon be possible to shorten tours of duty, the decision to do so has not been made yet."

The move to shorter deployments has been pushed by Gen. George Casey, Army chief of staff, as a way to reduce the strain on troops battered by long and repeated tours in Iraq and Afghanistan. But that goal has been hindered by the ongoing security demands in Iraq.

What the future holds for troops in Iraq will become clearer when Petraeus goes before congressional committees Tuesday.

Petraeus is expected to lay out his proposal for a pause in troop cuts after July when the last of the five additional brigades ordered to Iraq last year have come home. And he will likely tell lawmakers how many more troops could be withdrawn this year, as long as conditions in Iraq remained stable.

His presentation will include statistics reflecting the reduction in violence over the past seven months, but it will also note the latest spike in fighting in Basra, as Iraqi security forces took on Shiite militias, and the attacks that stretched out into Baghdad.

Petraeus and Crocker are expected to tout political advancements by the Iraqis, although they will note that much more needs to be done.

Officials said Friday that the Army proposal to reduce tours is on track. Top military leaders made it clear to Bush in a closed-door meeting late last month that they are worried about the war's growing strain on troops and their families.

Gates made the decision to extend deployments to 15 months last year, because that was the only way the Army could provide enough troops for the Bush-ordered military buildup aimed at quelling the violence in Baghdad.

Ever since, Gates, Casey and Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, have said they want to go back to 12 months tours as soon as possible.

There are now 158,000 U.S. troops in Iraq, including 18 combat brigades — down from a peak of 20 brigades for much of the past year. By the end of July, military leaders have said those numbers would fall to 140,000 troops, including 15 combat brigades.

Casey has said he could reduce combat tours if the demands on the Army were cut back to a total of 15 brigades in the war zone. At the end of July there would be 13 in Iraq — along with two Marine units — and two Army brigades in Afghanistan.

In a related move Friday, Democrats signaled that they don't see much hope in ending the Iraq war this year so long as Bush insists U.S. troops remain committed there in large numbers.

Still, party leaders wrote to Bush on Friday to tell him it's not too late to change course and plead with him not to leave the war for the next president to handle.

"We are deeply concerned that you and the congressional Republican leadership are intent on staying the current course throughout your administration and then handing the Iraq war off to future presidents," the Democrats wrote.

Others said they hope to see continued efforts to force troop withdrawals, but they acknowledged they were unlikely to succeed.

"I expect most of our troops to still be there" come the end of the year, said Sen. Carl Levin, D-Mich., chairman of the Armed Services Committee.

"Until there's either a big enough majority in the Senate or a change in the president's (approach), I don't see a significant improvement situation improvement in Iraq," Levin said in a conference call with reporters.

Sen. Joe Biden, chairman of the Foreign Relations Committee, predicted in the same conference call that the situation in Iraq will grow considerably worse by September "because the administration seems to have no political game plan."

Since Democrats lack a veto-proof majority, they have repeatedly failed to force Bush to accept any anti-war legislation, including one measure supported by many Republicans that would have required that troops spend more time at home between combat tours.

FOX News' Jennifer Griffin and The Associated Press contributed to this report.