The White House is rejecting as premature a plan by two senior Republican senators to restrict the mission of U.S. troops in Iraq

President George W. Bush's national security adviser, Stephen Hadley, said Sunday the administration has a "very orderly process" set out for reviewing whether its Iraq strategy is working and that it should be allowed to play out.

Asked in a broadcast interview whether Bush could live with the plan offered by Sens. John Warner and Richard Lugar, Hadley said, "No."

Warner and Lugar proposed legislation Friday that would give Bush until mid-October to submit a plan to limit the military mission in Iraq to protecting borders, fighting terrorists, protecting U.S. assets and training Iraqi forces.

Hadley said Bush is staying with his plan to evaluate progress in Iraq in September and decide on a course of action from there, without conditions.

"They've done a useful service in indicating the kinds of things that we should be thinking about," Hadley said of the senators. "But the time to begin that process is September.

"And the opening shot really ought to be to hear from the commanders on the ground who can make an assessment of where we are in our current strategy."

The Senate's Democratic leadership also is not very receptive to the Warner-Lugar proposal, but for different reasons. Democrats favor tougher steps to restrict Bush's options and get the troops out, but need more Republicans to peel away from Bush before they can prevail.

Sen. Carl Levin, chairman of the Senate Armed Services Committee, challenged even the mixed findings released by the White House last week on progress made by Iraqi leaders on a list of political and security reforms.

"This is not a half-full, half-empty issue," said Levin. "They have made no progress in the one key area that everyone agrees must have progress or the violence will not end, and that's on the political side of things. ... This is just a veneer and the veneer has worn away."

Levin has proposed legislation that would require most troops to be out by April 30.

Hadley said the administration is still pressing Iraqi lawmakers to cancel their monthlong vacation in August. The White House, however, seems resigned to seeing the break go forward, and he joined other Bush aides in playing down its significance.

Hadley noted Iraqi lawmakers plan to work six days a week until the end of July, and he said work will continue outside the parliament through August on sectarian reconciliation and power-sharing.

The parliament shortened its usual two-month break under pressure, but that has not appeased critics. They say Iraqi political leaders should not take a vacation that U.S. troops fighting in the blistering heat of summer do not get.

Lugar and Warner said their proposal asks that Bush start thinking now about different options and seek to boost diplomacy in the coming months. They cited an over-stretched military and growing terrorist threats around the world.

But that does not mean an abandonment of a U.S. presence in Iraq, they said.

"This nation of ours has got to remain in that area," Warner said, pointing to the United States' "vital security interests" involving Middle East oil and relations with Israel.

Hadley and Warner appeared on ABC's "This Week. Hadley and Levin spoke on " "FOX News Sunday."