A suicide attack on an Air Force bus that killed eight people on Thursday in Pakistan fuelled fresh speculation that General Musharraf could invoke emergency powers to postpone elections, due in or around January, which are meant to transform the country into a civilian-led democracy.

"I am not going to get into the details of our conversations but I think it would be quite obvious that the United States would not be supportive of extra-constitutional means," said Rice, when asked whether the United States opposed any move by Musharraf to declare martial law.

"Pakistan needs to prepare for and hold free and fair elections," said the top US diplomat, adding that she had not spoken to Musharraf in recent days.

Rice was speaking to reporters en route to Turkey and before a refuelling stop in Shannon, Ireland.

When speculation was rife several months ago that Musharraf was set to declare a state of emergency, Rice called him to make clear that this was a move Washington strongly opposed and there must be a move to civilian rule via democratic elections.

"The political space needs to be prepared by moderate forces, beginning to work together, which is why we have been supportive of moderate forces like Mrs. Bhutto's return, and that moderate forces have a common enemy in the extremists who are so much in evidence," Rice said.

Rice was referring to Pakistan's former prime minister and opposition politician Benazir Bhutto, who returned from exile to Pakistan last month. General Musharraf granted an amnesty that allowed Bhutto to return without fear of prosecution in graft cases hanging over her from the 1990s.

There is speculation the pair might end up sharing power after national elections and the United States, concerned about rising militancy in nuclear-armed Pakistan, is quietly fostering a partnership.