President Obama is days away from announcing a new Afghan strategy, but his immediate battle could come from liberals who are vowing to "spank" the president for committing tens of thousands of more troops to the eight-year conflict.

In a prime-time speech Tuesday from the U.S. Military Academy at West Point, Obama is expected to announce that he is sending up to 35,000 additional troops to Afghanistan beginning next year.

The figure is short of the 40,000 troops his top commander in Afghanistan, Gen. Stanley McChrystal, requested -- but enough to anger many congressional Democrats who oppose any potential troop surge, arguing that the mission is too expensive and lacks a clear objective.

"I think there will be some disillusionment within his base," said Paul Kawika Martin, political director for Peace Action, a grassroots organization, who added that thousands of activists are planning to protest following the president's announcement.

"We're going to spank him for sending more troops," he told FoxNews.com, adding that they may also "thank him" if he announces a quick exit strategy.

The White House has said that the U.S. won't be in Afghanistan for another eight or nine years. But that won't satisfy liberals, Martin said.

Even though Obama's announcement is sure to reawaken the anti-war movement, Martin said, the protests won't be as intense as they were in the Bush era because the movement has been weakened by the economic recession -- some organizations have shed up to 40 percent of staff in the past year, he said -- and is distracted by the national health care debate. He also said many members of the movement voted for Obama and trust him more than the Bush administration.

"So you don't have that same type of anger," he said.

But without the support of congressional Democrats, Obama will find himself in the awkward position of relying on the support of Republicans who largely oppose his domestic agenda. And he may have to explain how he supports a troop surge in Afghanistan when he opposed one in Iraq two years ago.

Republicans, though, see the announcement as a chance for Obama to finally work with both political sides.

"The president does face a serious battle inside his own caucus, his own party, particularly in the House of Representatives," former senior Bush adviser Karl Rove told Fox News. "But here's a moment for bipartisanship. I suspect the president will easily win support for this if he reaches out and melds together the Democrats who are willing to support his war policy with the Republicans. I suspect virtually every Republican will support the president in this if he asks for their support."

Before Obama speaks Tuesday, he is meeting at the White House with all the Democratic chairmen of the relevant committees along with their Republican counterparts.

Two top Democrats have already said they will push for a "war surtax," a new tax on the wealthy to pay for any increase in U.S. troops for the war.

Rep. David Obey, D-Wis., chairman of the powerful House Appropriations Committee, which controls the pursestrings for the war, and Sen. Carl Levin, chairman of the Senate Armed Services Committee, are making the demands.

"If we have to pay for the health care bill, we should pay for the war as well ... by having a war surtax," Obey told ABC News this week. "The problem in this country with this issue is that the only people that has to sacrifice are military families and they've had to go to the well again and again and again and again, and everybody is blithely unaffected by the war."