The Saudi authorities have asked Nawaz Sharif not to return to Pakistan to seek power next week - but the exiled former Prime Minister has said he is going anyway.

In a rare public intervention in the internal affairs of another Muslim country, a Saudi official has reminded Mr Sharif that he gave his word of honour seven years ago not to return to Pakistan for a decade.

“Wisdom demands that Mr. Nawaz Sharif commit himself to the promises he made; namely, not to return to Pakistan and to political activity,” the Saudi Press Agency quoted the unnamed official as saying.

But Sadique ul-Farooq, a spokesman for Mr Sharif’s Pakistan Muslim League (N) party, said today that the former premier had won the legal right to go home and would return to Islamabad as planned.

Mr Sharif’s aim is to unseat President Pervez Musharraf, whose once firm grip on power has been weakened by a violent Islamic insurgency, loss of support among Pakistan moderates and growing criticism among his allies abroad.

Mr Sharif's own elected Government was ousted by General Musharraf in a 1999 military coup. The following year Mr Sharif was convicted by a Pakistani court of hijacking and sedition, and sentenced to life in prison.

But after an intervention by Crown Prince Abdullah - now the King of Saudi Arabia - who gave personal assurances to guarantee Mr Sharif's conduct, he was instead allowed to go into exile in Saudi Arabia.

Last month that arrangement was left in tatters, when Pakistan's Supreme Court said that Mr Sharif had an “inalienable right" to come back, and that the Government would be in contempt of court if it tried to stop him.

The prospect of his return has already triggered unrest in Pakistan. About 50 supporters of Mr Sharif were rounded up and detained by Pakistani police yesterday, in a move condemned by his party.

His return has also caused embarrassment in Saudi Arabia, according to Zahid Hussain, Times correspondent in Islamabad. "They have been put in a highly embarrassing position, because it was only because of the personal intervention of King Abdullah that Pakistan agreed to send him to Saudi Arabia," said Hussain.

"They were under an obligation to keep him there, and that is why Saudi Arabia has asked him not to return: because otherwise they have failed in their undertaking."

One option for General Musharraf is to allow Mr Sharif to land and then to bundle him straight onto another plane out of the country, Hussain added. Another would be to fling Mr Sharif in jail - the Government has reserved the right to revive the life sentence, and also a string of tax evasion charges that were dropped. Both were however likely to cause further unrest.

There was personal bad blood between General Musharraf and Mr Sharif, added Hussain. The President was angered that Mr Sharif once refused to allow his plane with 200 other passengers on board to land, until it was forced to make an emergency landing with five minutes of fuel left: while Mr Sharif resented General Musharraf for ousting him from power and throwing him into jail.

Mr Sharif’s expected return comes at a time of political ferment in Pakistan, as General Musharraf tries to strike a deal with another exiled former prime minister, Benazir Bhutto, that could see him cling on to power and bring her back into government.

Both Ms Bhutto’s party and the Government have reported progress in the latest round of talks held in Dubai yesterday, after earlier difficulties. Ms Bhutto is insisting that if she is to seek re-election on a joint ticket with General Musharraf, he must quit the army. Today she claimed that the matter was "resolved".

The pair are trying to negotiate a deal that would allow General Musharraf to ask MPs to elect him to a new five-year presidential term by October 15, while allowing Ms Bhutto to return to Pakistan and contest parliamentary elections due by January 2008.

"The negotiations are not over, a final deal has not been reached yet," said Hussain, after interviewing Ms Bhutto this afternoon.

"My gut feeling is that ultimately it will be done, because Musharraf needs it more than ever before. He can't take on both opposition leaders.

"And there is huge pressure behind the scenes from the United States and Britain to reach some power-sharing arrangement to prevent further damage being done by extremist groups."

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