Former foreign minister Abdullah Abdullah withdrew from a presidential election run-off vote planned for November, saying it could not be conducted freely or fairly. (Jerry Harmer/Associated Press)

Afghan President Hamid Karzai's chief political opponent says the current government will not be able to live up to its promise to stamp out corruption because it cannot be trusted to follow the rule of law.

Former foreign minister Abdullah Abdullah said Wednesday Karzai's government has squandered eight years of international assistance and during that time has failed to rein in corruption or establish institutions capable of meeting the needs of the Afghan people.

"That government cannot bring legitimacy, cannot fight corruption," Abdullah said, adding that it "cannot deal with all the challenges, especially the threat of terrorism, security problems, poverty, unemployment and many others."

Abdullah said the Afghan election commission's decision to declare Karzai the winner of the election and cancel a planned run-off vote was not legal.

The run-off was scheduled to be held this month after the first round of voting was marred by widespread fraud, but Abdullah dropped out because he said the run-off could not be conducted freely or fairly until changes were made to the commission.

He said, however, that he was not personally challenging the ruling.

"The process has completed itself with that final, illegal decision," he said, referring to the election commission's ruling.

"I leave it to the people of Afghanistan to judge," he said.

International forces under fire

Abdullah's comments came a day after five British soldiers were killed in Helmand's Nad-e-Ali district when an Afghan police officer opened fire on them. A month earlier, an Afghan policeman on patrol with U.S. soldiers opened fire on American troops, killing two.

Abdullah said the continuing violence showed that Karzai's administration has failed to bring peace despite international assistance.

The incidents are a blow to the NATO strategy of training and operating jointly with Afghan police and soldiers in the hopes they might be able to deal with the spreading Taliban-led insurgency without international assistance.

The August presidential election was seen as crucial to strengthening the credibility of the Afghan government in the eyes of both its citizens and international allies, many of whom —particularly the United States — are considering sending more troops to the embattled country, where Taliban and al-Qaeda insurgents still control many regions.

Karzai tried to put international leaders at ease on Tuesday, vowing to banish corruption.

Afghanistan "has a bad name from corruption," the president said. "We will do our best through all possible means to eliminate this dark stain from our clothes."

Karzai has said he was open to working with other political leaders, and people close to Karzai have said he and Abdullah have been in talks about a power-sharing agreement. But Abdullah on Wednesday said he does not want a place in Karzai's government.

"In this environment I would rather act like a pressure group," Abdullah said.

With files from The Associated Press