Some 18,000 American troops have started a winter offensive against Taliban (search) rebels in Afghanistan, vowing to eliminate insurgents who could threaten parliamentary elections slated for the spring.

The U.S. military said Saturday that it hoped the new push, dubbed Lightning Freedom (search), would persuade insurgents to accept an amnesty offered by President Hamid Karzai that could stabilize the country and allow foreign troops to pull back.

"It's designed basically to search out and destroy the remaining remnants of Taliban forces who traditionally we believe go to ground during the winter months," spokesman Maj. Mark McCann said. "It's going on throughout the country of Afghanistan."

The operation was initiated after Karzai's inauguration Tuesday as the country's first democratically elected president, McCann said. He didn't know exactly when it began and gave no details of any specific moves against militant targets.

But Maj. Gen. Eric Olson, the No. 2 American commander here, told The Associated Press last month that the operation would include a redeployment to tighten security on the border with Pakistan (search) and raids by special forces to snatch rebel leaders.

Protecting Afghanistan's young democracy has become the most urgent priority for American commanders frustrated by their failure to capture Al Qaeda leader Usama bin Laden, who disappeared after the Sept. 11, 2001, attacks in the United States.

The landmark Oct. 9 vote, which gave a landslide victory to Karzai, was free of the major violence threatened by Taliban diehards, who continue to fight on three years after being ousted from power. Attention is already turning to the more complex National Assembly election, slated for April.

The new military drive, which involves the entire 18,000-strong U.S.-led force here, also is aimed at persuading militants to take up an offer of amnesty from the American military and the Afghan government, McCann said.

Lt. Gen. David Barno, Olson's superior, told AP last week that if a large number of Taliban foot soldiers give up the fight in return for a promise that they can return to their villages, U.S. troop strength could be cut by next summer — once the parliamentary election is complete.

McCann said the military believes the operations "will establish security conditions that allow the parliamentary elections in the spring to occur with the same success" as October's vote.

Lightning Freedom represents a new phase, rather than any shift in strategy, and commanders will continue mixing combat operations with humanitarian actions, the spokesman said.

Compared with last winter, the United States has several thousand more troops strung out across the south and east, where insurgents are strongest.

McCann said the U.S. military will also help Afghan forces combat the country's booming drug industry by sharing intelligence, ferrying counter-narcotics units to and from raids, and rescuing them if they get into serious trouble.

Karzai says exploding cultivation of opium poppies, the source of most of the world's heroin, is now a bigger threat to the country than militants. Officials are vowing to arrest top smugglers and refiners next year.

However, the U.S. military is concerned that raids could lead to fresh political instability and will lend a hand to anti-drug raids "as long as they do not interfere with the coalition's primary missions" of defeating insurgents and fostering reconstruction, McCann said.

The number of so-called Provincial Reconstruction Teams — small military units tasked with supporting local authorities and carrying out small-scale relief and development projects — has also risen from five to 19 over the past year.

"It's not just about conducting combat operations. It's also about connecting with the people here," McCann said.

The new operation follows Lightning Resolve, a massive security operation begun in July to protect the October election, the first national vote since the fall of the Taliban in late 2001.

In previous winters, the U.S. military has mobilized one or two battalions for sweeps of particular regions, an approach which brought few visible results.