US President George W. Bush on Monday said that he had signed an executive order freezing the assets of 27 individuals and organisations he said were linked to terrorists.

Addressing a press conference at the White House, Mr Bush said the list was the "financial equivalent of law enforcement's 'most wanted' list" and included "terrorist organisations, individuals, terrorist leaders, a corporation that serves as a front for terrorism and several non-profit organisations".

"We're putting banks and financial institutions around the world on notice" that they must freeze the assets and cease all business with those on the list or risk repercussions from the US, Mr Bush said. He said he expected the majority of assets seized to be outside the US.

"If you do business with terrorists, you will not do business with the United States of America," Mr Bush said.

Paul O'Neill, US treasury secretary, who also addressed the press conference, said financial institutions had two options - co-operate or be punished.

Mr Bush said that more names would join the list of 27 issued under Monday's executive order. The treasury department said last week it had set up a Foreign Terrorist Asset Tracking Center to try to locate the source of funds for terrorist organisations.

The list published on Monday includes organisations from across North Africa, the Middle East and Central Asia.

The government had indicated at the weekend that it planned to release to the public soon information linking Mr bin Laden to the attacks.

The mayor, who attended an emotional memorial service for the missing on Sunday, refused to speculate on his future as pressure grows for him to stay on as mayor.

Mr Giuliani is approaching the end of his second term as mayor and city laws forbid him to serve a third term. The first round of voting to select a Democratic mayoral candidate begins on Tuesday, the polls were postponed from September 11 in the wake of the attacks.

Mr Giuliani, a Republican, has urged people to take part in the vote.