According to diplomatic sources, the demand was made in a telephone call by US Secretary of State Hillary Clinton to the Minister for Foreign Affairs, Hina Rabbani Khar.

Even as the FO release said the conversation between the two ministers was about “carrying forward the trajectory of bilateral relations”, Ms Khar’s meeting with the prime minister after Ms Clinton’s call followed by Interior Minister Rahman Malik’s meeting with Mr Gilani, added to speculations that Washington was ratcheting up pressure for getting Mr Weinstein released.

Secretary Clinton and Ms Khar also discussed Mr Gilani’s expected meeting with Ms Clinton on the sidelines of UN General Assembly session next month.

The flurry of meetings on Thursday was preceded by Ambassador Cameron Munter’s meeting with Ms Khar a day earlier.

The meetings coincided with a statement by Punjab Home Minister Rana Sanaullah that Mr Weinstein was engaged in mysterious activities like those of CIA contractor Raymond Davis. The statement is said to have sent alarm bells ringing in Washington.

Police also released a sketch on Thursday of  Mr Weinstein’s possible  abductor.

The American was abducted from his residence in Lahore last weekend by gunmen.

So far there has been no lead in the case as abductors haven’t made any demands as yet.