KABUL, Afghanistan — Less than 25 percent of Afghans say the national police are now strong enough to handle security without international forces' help, but three-quarters believe they will be ready by the 2014 NATO handover, according to a U.N. survey released Tuesday.

Support for the NATO military force staying in the country also appeared widespread more than 10 years into the U.S.-led campaign. Sixty-eight percent of those surveyed said foreign troops should stay for the time being, compared to about a quarter who said they should leave immediately.

Strengthening the Afghan army and police to fend off the Taliban insurgency is key to NATO's plans to turn over security responsibility by the end of 2014. The U.S.-led coalition is sponsoring efforts to expand the national police from about 100,000 two years ago to 157,000 by October. Training that many police so fast has faced problems, including illiteracy among recruits and complaints of corruption and abuse.

According to the annual Police Perception Survey, about 21 percent of those polled said Afghan police were ready to handle security and crime-fighting on their own now, with a further 54 percent saying they would be strong enough within two or three years — roughly coinciding with the NATO handover deadline. The rest said police wouldn't be ready even in three years or gave no opinion.

Three-quarters of respondents said the Afghan National Police are "at least somewhat effective" at fighting insurgents, up five points from the previous year.

NATO and Afghan officials welcomed the results of the poll, sponsored by the U.N. Development Program and the Afghan Interior Ministry, saying it shows progress is being made.

"The training of Afghan police in the last 12 months has significantly improved," Interior Minister Bismullah Khan Mohammadi said, adding that it "has produced positive and tangible results."

Brig. Gen. Carsten Jacobson, a NATO spokesman in Kabul, also said the survey shows trends moving in the right direction.

"It definitely shows there are fields where Afghan security forces continue to need improvement, but ... looking at the continuation of progress over the last years is really encouraging," he said.

Fifty-three percent of Afghans polled in the U.N. survey said the national police are somewhat or very corrupt, down from 60 percent in the same survey last year. And nationwide, about 74 percent of those polled expressed personal confidence in the national police in their area, up 3 percentage points from last year's poll.

Asked when most international troops should leave Afghanistan, 21 percent of respondents said at the end of 2014 as planned, while 23 percent said "once the Taliban has been defeated" and 24 percent once Afghan security forces have been trained to fight the insurgency on their own. Twenty-four percent wanted an immediate withdrawal and 6 percent favored an indefinite international military presence.

The survey, conducted by an independent research firm, polled more than 7,000 Afghans in October in all 34 of Afghanistan's provinces, although some randomly chosen districts were inaccessible because of the threat from Taliban insurgents. It had a margin of error of 1.6 percentage points.

Also Tuesday, a NATO service member was killed in an insurgent attack in southern Afghanistan, the coalition said in a statement, which provided no other details. The death brings to 33 the number of international troops killed this month in the country.