Security has been stepped up in New York and Washington over a possible bomb threat to coincide with the 10th anniversary of the September 11 attack on Sunday. Police have increased patrols of possible target sites and has been searching vehicles causing big traffic jams. Secretary of State Hillary Clinton said the threat is credible and involved Al Qaeda and that everyting is being done to protect the people. Speaking after she attended 9/11 commemorations at the New York Stock Exchange, Mrs Clinton said, there has been a “specific, credible but unconfirmed report” of an attempt to target New York and Washington DC. President Barack Obama is to visit New York and Washington tomorrow as the US marks 10 years since al-Qaeda attacked. Nearly 3,000 people died in New York , Washington and Pennsylvania in 2001.