ISLAMABAD (AFP) - Pakistani military ruler Pervez Musharraf girded Sunday for a Supreme Court battle over whether he can claim victory in a presidential vote, a confrontation which could further destabilise the country.

The key US ally, at the centre of international efforts to combat Islamic extremism, swept to an overwhelming majority in Saturday's controversial election after it was boycotted by almost the entire opposition.

The country's top court is however weighing up the legality of the poll and whether Musharraf was allowed to stand while keeping his role as army chief, ruling on Friday that the result cannot be confirmed until it decides.

A judgment against the general, who grabbed power in a bloodless coup in 1999, could push Musharraf over the brink after months of political turmoil and make him declare martial law.

Musharraf late Saturday insisted that his "great victory" was democratic, rejecting claims that abstentions by former premier Benazir Bhutto's party and resignations by other opposition MPs made it illegitimate.

"Democracy means majority, whether there is opposition or no opposition," he told reporters.

But he refused to rule out emergency action if the court overturns the result, saying: "Let them come to their decision, then we will decide."

The court says it will start hearing the challenges against the election on October 17, the end of the Muslim festival of Eid-ul-Fitr and the day that Bhutto is due to board a plane back to Pakistan after years in exile.

Musharraf signed an amnesty deal for two-time prime minister Bhutto on Friday, as a prelude to a power-sharing deal ahead of a general election that is due by January 15 at the latest.

A source close to the presidency was more blunt, saying that the president could impose "surgical martial law" to maintain stability in the nuclear armed nation the event of an unfavourable court ruling.

The United States, which has closely watched the election process amid a recent rash of Islamic extremist violence, gave cautious congratulations to the Pakistan nation, but withheld comment on Musharraf's win.

"Pakistan is an important partner and ally to the United States and we congratulate them for today's election," White House spokesman Scott Stanzel said, refusing to discuss the victor until an official declaration.

With Musharraf's fate in the court's hands, his vow to step down as head of the army by the end of his current five-year term on November 15 now appears to be in limbo.

He is due to swear in his designated successor as army chief, former intelligence chief Ashfaq Kiyani, on Monday, but the court row has quashed speculation that Musharraf might hang up his uniform immediately afterwards.

Musharraf's supporters freely celebrated his win in the vote by the two national houses of parliament and four provincial assemblies by setting off fireworks, despite the delay in the announcement of official results.

Chief election commissioner Qazi Mohammad Farooq said a total of 257 votes were cast in the national assembly and senate, out of which Musharraf bagged 252 and three were rejected.

One rival, former judge Wajihuddin Ahmad, won two votes, he said. Another, Makhdoom Amin Fahim, vice-chairman of Bhutto's Pakistan People's Party, got none.

Musharraf's total electoral college vote, including the provincial assemblies, was 384 ballots out of 702, government officials said on condition of anonymity.