WASHINGTON (Reuters) - The top Republican on the Senate Armed Services Committee urged President George W. Bush on Sunday to go before the American public to explain his plan for the war in Iraq.

Virginia Sen. John Warner (news, bio, voting record) told NBC's "Meet the Press," said such a public address would be helpful to hold on to public support during the next six months while Iraq sets up its own government and gains the ability to maintain its security.

Bush, who has been out of public sight since he arrived on November 22 at his Crawford, Texas ranch for a Thanksgiving break, has been facing waning support for the war and the lowest job approval ratings of his presidency.

"I think it would be to Bush's advantage. It would bring him closer to the people, dispel some of the concern that, understandably, our people have about the loss of life and limb, the enormous cost of this war to the American public," Warner said.

"We have got to stay firm for the next six months. It is a critical period ... in this Iraqi situation, to restore full sovereignty in that country. And that enables them to have their own armed forces to maintain that sovereignty," he said.

Bush is to speak on immigration in Arizona on Monday and then will return to Washington on Tuesday and give a speech about the war on terror at the U.S. Naval Academy in Annapolis on Wednesday.

Anti-war protesters, including Cindy Sheehan whose son died in Iraq last year and who became an icon for the peace movement after her 26-day vigil near Bush's ranch in the summer, gathered in the tiny central Texas town again, although in much smaller numbers. They vowed to come to Crawford every time Bush visits his ranch.

Warner was one of the authors of a Senate-passed resolution that called for Iraqis to start taking the lead in their own security next year to allow a phased withdrawal of U.S. troops.

CRITICAL SIX MONTHS

While the Senate rejected a Democrats' demand that Bush submit a plan and an estimated timetable to withdraw, Democratic Sen. Joe Biden of Delaware said on NBC it would be "virtually impossible" to sustain 150,000 American troops in Iraq for the next two years.

Although Biden said he did not believe the Iraq war was lost, he added: "I think we have a six-month window here to get it right. But I have to admit that I think the chances are not a lot better than 50-50."

Senate Foreign Relations Committee chairman Richard Lugar, said on "Fox News Sunday" that more pressure needs to be put on the Iraqis to take responsibility for their security.

"But the fact is that we are going to try to train them to perform, and the question is how well they do so, whether they mop up on each other or whether they have a unified country," the Indiana Republican said.

Iraq's national security adviser, Mowaffaq al-Rubaie, said the goal was to enable multinational forces to be drawn down to under 100,000 by 2007.

"Basically, we want to create the right conditions in the urban areas for the Iraqi security forces to assume the responsibility of security in these cities and towns," he said on CNN's "Late Edition."

U.S. defense officials said last week that the Pentagon plans to shrink the U.S. troop presence in Iraq, now at 155,000, to about 138,000 after the December 15 Iraqi elections and is considering dropping the number to 100,000 next summer if conditions allow. However, a variety of scenarios are being reviewed, including no troop cuts, based on political and security conditions in Iraq.

(Additional reporting Leslie Wroughton in Washington and Patricia Wilson in Crawford, Texas)

Commentary: