WASHINGTON — US public perceptions of Pakistan and Afghanistan have sunk to new lows as the war campaign against Islamic extremism approaches its 10th year, a poll said Friday.

Some 14 percent of Americans have a favorable view of Afghanistan and 82 percent hold a negative review, the Gallup poll said. For Pakistan, 18 percent saw the country favorably and 76 percent viewed it unfavorably.

The views were the most negative since Gallup began asking the question. Opinion about the two nations peaked in 2005, when upwards of 40 percent of Americans saw both Afghanistan and Pakistan in a positive light.

The United States has had uneasy partnerships with the two nations, with US officials increasingly questioning the reliability of Afghan President Hamid Karzai and elements of the Pakistani establishment.

Separate polls have shown low US support for the war in Afghanistan, as well as strongly unfavorable views of the United States in Pakistan.

The Gallup poll, which surveyed 1,015 US adults, also found that US opinion of South Korea has reached a new high, with 65 percent seeing the Asian ally favorably.

US relations with South Korea have improved markedly since conservative President Lee Myung-Bak took office in 2008. The United States and South Korea have finalized a free trade deal first negotiated by earlier administrations.

The most popular Asian nation among the US public remained Japan, with 80 percent of Americans holding a favorable view, in line with findings in recent years.

Americans had higher opinions only of Canada, which 92 percent saw favorably, along with Britain and Germany.

Despite a year of friction with China on trade and other issues, US perceptions rose slightly, with 47 percent of Americans seeing the rising Asian power favorably, compared with 42 percent a year earlier.

The worst-viewed nations were North Korea and Iran, with only 11 percent of Americans seeing each country in a favorable light.

The poll had a margin of error of four percentage points.