Pentagon has earmarked 10 more combat brigades with 35,000 troops for deployments in Iraq this year, in order to maintain the ongoing military buildup there.

Pentagon spokesman Bryan Whitman told reporters that the order, signed by Defense Secretary Robert Gates, does not mean that the increased level of 20 combat brigades in Iraq will be kept through year-end.

"This deployment announcement of the next 10 units that are in the queue has nothing to do with a decision to extend the surge," Whitman said.

Rather, the move is aimed at maintaining the ongoing buildup plan announced by President George W. Bush in January, he said.

"The (Defense) Department has made very clear that decisions on the surge will depend entirely upon conditions on the ground," Whitman added.

Bush's plan is to send 30,000 additional troops to Iraq to pacify the violence-prone areas including Baghdad.

The 10 combat brigades will begin deployments this fall and will stay in Iraq for up to 15 months.

Some 1,000 additional support troops will also be deployed in August.

The latest deployment decision came at a time when congressional leaders from both parties are giving Bush a matter of months to prove if his buildup plan really works, with September looking increasingly like a decisive deadline.

In that month, political pressure in Washington is expected to dovetail with the military timeline in Baghdad.

David H. Petraeus, the top U.S. commander in Iraq, will by then to tell lawmakers if the current buildup plan has any impact on Iraq's political process.

Also, as the new fiscal year will begin Oct. 1, the Congress is set to place tough new strings on war funding.