The U.N. peacekeeping chief said Monday it would be "almost impossible" to hold a fair election in Afghanistan before July, months after the early spring vote that President Hamid Karzai is seeking.

Alain Le Roy said the Aug. 20 date set by Afghanistan''s Independent Election Commission in January is "very credible and very reasonable." An earlier vote would be "very difficult to organize," mostly for logistical and technical reasons but also because of security needs, he said.

Karzai suddenly issued a decree Saturday directing the election commission to set a date that adheres to the Afghan constitution, which calls for a ballot 30 to 60 days before the May 22 expiration of the president''s five-year term.

Political opponents accused Karzai of "sabotage" by trying to rush the vote. The move was widely viewed in Kabul as a political gambit to give Karzai the high ground in a tussle for power after May 22, when opponents say they will no longer recognize him as president.

The election is likely to be the most dangerous since a U.S.-led invasion ousted the Taliban''s Islamist regime in late 2001. The militant movement, which has regained control of large swaths of the country, said it will not participate — and warned other Afghans not to.

The international community, led by the United Nations, ran the presidential election in 2004 that brought Karzai to power and the government has asked the U.N. to provide technical expertise to the Afghan commission for this year''s election.

In setting an Aug. 20 election, the commission said the vote could not be held sooner because of security concerns, heavy spring snows in the Afghan mountains and ballot distribution issues.