By M Ilyas Khan
BBC News, Karachi
Saudi Arabia has asked Pakistan's exiled ex-PM Nawaz Sharif not to return to the country, citing a commitment he made in 2000, local media say.
Mr Sharif was deposed in a coup
Mr Sharif's government was overthrown in a military coup in 1999, and he was exiled to Saudi Arabia in 2000.
He has announced his plans to return home on 10 September to challenge President Pervez Musharraf.
His return poses the most serious threat to an increasingly fragile government, led by Gen Musharraf.
Last month, Mr Sharif filed a petition in the supreme court pleading his right to return to Pakistan.
The court upheld the petition, overruling documents produced by the government that showed Mr Sharif had undertaken to stay away from the country for 10 years.
'No change of plan'
Recent media reports claim that Gen Musharraf has made several presentations to the Saudi government seeking their help in preventing Mr Sharif's return.
The Pakistani authorities have been indicating that the exile deal with Mr Sharif was struck with the mediation of some Saudi dignitaries.
MUSHARRAF UNDER PRESSURE
9 March: Musharraf suspends chief justice for "abuse of power". Lawyers protest
April: Protests grow, amid clashes with police
12 May: 34 people die as rival political groups clash in Karachi
11 July: 102 people die when army storms radical Red Mosque in Islamabad
July-Aug: Sharp rise in suicide attacks by pro-Taleban militants
20 July: Supreme Court reinstates chief justice
9 Aug: Musharraf rejects emergency rule
23 Aug: Supreme Court says exiled ex-PM Nawaz Sharif can return
The official Saudi Press Agency on Tuesday quoted an unnamed government spokesman as saying that Mr Sharif should fulfil his promises.
"Wisdom demands that Mr Nawaz Sharif commit himself to the promises he made - namely, not to return to Pakistan and to political activity," he said.
He denied Pakistani media reports that Saudi Arabia had expressed "satisfaction and support" for the return of Mr Sharif and his family to Pakistan.
The spokesman said the Saudi government agreed to receive Mr Sharif in 2000 "as a humanitarian gesture".
A spokesman for Mr Sharif's PMLN party in London said the former prime minister's travel plans to Pakistan were not subject to any change.
Mr Sharif served two terms as prime minister in 1990-93 and 1997-99.
He was sentenced to life in prison for offences including tax evasion and treason after the 1999 coup.
Pakistani authorities say Mr Sharif promised to stay out of the country and away from politics for 10 years in exchange for his freedom.
But last week the country's Supreme Court ruled that he and his family had "an inalienable right to return and remain in the country as citizens of Pakistan".