WASHINGTON - Defense Secretary Robert Gates blamed the Taliban's revival on a past failure to deploy enough troops to Afghanistan and said U.S. forces would not withdraw whatever the result of President Barack Obama's strategy review.

We are not leaving Afghanistan. This discussion is about next steps forward and the president has some momentous decisions to make, Gates said in a TV program taped at George Washington University on Monday and being aired by CNN on Tuesday.

Obama faces pivotal decisions after the top U.S. and NATO commander in Afghanistan, General Stanley McChrystal, presented a grim assessment of the eight-year war.

Eight American soldiers were killed last Saturday when tribal militia stormed two combat outposts in eastern Afghanistan, the worst U.S. loss in more than a year.

The administration is debating whether to send up to 40,000 more troops, or scale back the mission and focus on striking al Qaeda cells, an idea backed by Vice President Joe Biden.

Gates suggested U.S. and allied failure to put more troops into Afghanistan in the past, when then-president George W. Bush shifted resources to invade Iraq, gave the Taliban an edge.

Because of our inability, and the inability, frankly, of our allies, (for putting) enough troops into Afghanistan, the Taliban do have the momentum right now, it seems, Gates said.

Complicating the White House discussions are allegations of vote fraud in Afghanistan's August presidential election, mostly aimed at incumbent and provisional winner Hamid Karzai.

Some say if Karzai is declared victor despite the charges it will undermine his government's legitimacy. U.S. officials have cited the fraud allegations as a reason for the policy review.

VOTE COUNT RULES MAY HELP KARZAI

Afghan election authorities began a recount on Monday, but new rules appeared to make it unlikely Karzai's preliminary win would be overturned and a second round vote take place.

The former deputy head of the U.N. mission in Kabul, U.S. diplomat Peter Galbraith -- sacked last week for outspoken views on voting fraud -- said the method chosen to evaluate suspicious ballots was not acceptable.

The new rules from the U.N.-backed Electoral Complaints Commission treat suspicious ballot boxes the same regardless of which candidate received the suspect votes.

Galbraith told Reuters: It cannot be correct to treat all presidential candidates equally for disqualification of ballots.

Let's not mince words: there was one candidate who had control of the state apparatus.

A final result from the poll will likely come next week.

Galbraith is close to Richard Holbrooke, Obama's Afghanistan and Pakistan point man. Holbrooke is not considered a Karzai fan and is presumably a key player in the White House talks.

But more than Afghanistan politics are at issue in the talks.

In his CNN remarks, Gates said the United States could not afford to give al Qaeda and the Taliban the propaganda victory of a U.S. retreat in Afghanistan, where mujahideen forced the Soviet Union to withdraw after a decade of bloody warfare.

That country, and particularly the Afghanistan-Pakistan border, is the modern epicenter of jihad, he said.

And their view is ... they now have the opportunity to defeat a second superpower, which more than anything would empower their message and the opportunity to recruit and fund raise and plan operations.

What's more important than that in my view is the message that it sends that empowers al Qaeda, Gates said. The notion that they have come back from this defeat, come back from 2002, to challenge not only the United States but NATO, 42 nations, is a hugely empowering message should they be successful.

With casualties rising, U.S. public opinion has turned increasingly against what Obama's aides once called the good war, in contrast to the Iraq war launched by Bush in 2003.

Seeking to shore up support, Obama invited senior Democratic and Republican lawmakers to the White House on Tuesday to discuss the war. He will meet his national security team to continue the policy review on Wednesday and Friday.

Obama almost doubled the U.S. troop total in Afghanistan to 62,000 to combat the worst violence since U.S.-led forces ousted the Taliban rulers in 2001. The U.S. invasion was in response to the September 11 attacks carried out by al Qaeda, which had been given a haven in Afghanistan by the Taliban.

(Additional reporting by Peter Graff and Sayed Salahuddin in Kabul and Phil Stewart and Arshad Mohammed in Washington; Editing by Alan Elsner and Jerry Norton)