Support for the US mission in Afghanistan has slipped to a new low, with 44 percent of Americans now saying the war there has been worth the cost, according to a recently released poll.

Amid mounting divisiveness over what was once one of President Barack Obama's top foreign policy issues, the poll by The Washington Post and ABC News also showed ratings for how he has handled the mission there eroding, to 45 percent approving of how he is dealing with Afghanistan and 47 disapproving, compared to 63 percent approval last year.

The numbers come as Obama grapples with whether to send more US troops to Afghanistan to boost the fight against a growing Taliban-led insurgency, just a week after a stopover at a US military base in Alaska at the start of his Asia trip when he told US troops he will get "public support back home" for the mission.

Only 44 percent now say the war in Afghanistan has been worth fighting -- the fewest since early 2007 -- and 52 percent say it has not, up 13 points from its low of last December, the news outlets' polling divisions said.

And while 55 percent expressed confidence that Obama will forge a successful Afghan strategy, Americans appeared evenly split on whether the president should order large numbers of new troops into the country, with 46 percent supporting a larger US force and 45 percent a smaller one.

Just as many also appeared to trust Republicans in Congress to handle the war as trust the president.

While divisions were evident about the war, Americans clearly doubted the reliability of the government of Afghan President Hamid Karzai, who was declared winner of a second term this month after a fraud-marred election.

"Just 26 percent of Americans see Karzai as a reliable partner for the United States, and just 38 percent think his government will be able to train an effective army to take over security at some point," ABC News reported.

As for whether the risk of a terrorist attack in the United States would rise or fall if US troops withdraw from Afghanistan, nearly two-thirds of Americans said the risk stayed the same whether or not the troops went home.

The poll of 1,001 residents was conducted by telephone and has a margin of error of 3.5 percentage points.