Clinton: al Qaeda behind unconfirmed threat to U.S.

New York Police Department Inspector James Kehoe stands in the street and directs a ''Critical Vehicle Response'' deployment in New York, August 24, 2011.

WASHINGTON (Reuters) - U.S. Secretary of State Hillary Clinton on Friday said that al Qaeda was behind a specific, credible but unconfirmed report of a threat to harm Americans, notably in New York and Washington.

"We are meeting here in New York ... with the news last night of a specific, credible but unconfirmed report that al Qaeda again is seeking to harm Americans and in particular to target New York and Washington," Clinton said in a speech.

President Barack Obama on Thursday ordered a redoubling of counter-terrorism efforts in the face of the threat ahead of Sunday's 10th anniversary of the September 11, 2001 attacks on New York and Washington, U.S. officials said.

In a speech ahead of the anniversary, Clinton said it was impossible to foil every plot and that al Qaeda was still capable of regional and international attacks.

However, she said Washington would wage a "relentless" campaign against it and, later this month, would set up Global Counter-Terrorism Forum to gather officials to identify threats, devise solutions and share expertise.

The group, to be co-chaired by the United States and Turkey, will also include Algeria, Australia, Canada, China, Colombia, Denmark, Egypt, the European Union, France, Germany, India, Indonesia, Italy, Japan, Jordan, Morocco, The Netherlands, New Zealand, Nigeria, Pakistan, Qatar, Russia, Saudi Arabia, South Africa, Spain, Switzerland, the United Arab Emirates and the United Kingdom, the State Department said.

(Editing by Sandra Maler)