WASHINGTON - The United States is considering to put the Pakistani Taliban on the U.S. list of "foreign terrorist" groups, a State Department spokesman said Tuesday. The move would trigger punitive measures such as freezing assets tied to the militant group, barring foreign nationals with links to it from entering the United States and making it a crime to give any material help. "It is something we are considering in light of what happened, and obviously the investigation will yield information that might give us greater clarity," the department spokesman, P.J. Crowley, told a news briefing. Senior Obama administration officials have linked Faisal Shahzad, the suspected New York's Time Square bomber, to the Pakistani Taliban, a view contested by Pakiastan's U.N. Ambassador Abdullah Hussain Haroon. The envoy said in a CBS television interview that the attempted bombing in New York does not have the signature of the Taliban. Crowley said there was a lengthy legal process before a group could be designated a "foreign terrorist organization" and he did not know when a decision would be made. "We have been focused on this group for some time and, without being specific, we have been working with our Pakistani counterparts and we have taken appropriate action to diminish the capabilities of this group and others in the region," Crowley said, referring to military action to target Pakistani Taliban leaders. Shahzad, 30, a naturalized U.S. citizen born in Pakistan, was arrested two days after authorities say he parked a sport utility vehicle packed with a bomb in New York's busy Times Square on May 1. Five Democratic U.S. senators sent a letter to Secretary of State Hillary Clinton on Tuesday urging her to ensure the Pakistani Taliban was on the list. "The Pakistani Taliban is a murderous organization dedicated to killing civilians, harming U.S. interests in the region and has even taken credit for terrorist acts committed on U.S. soil," the senators wrote. There are 45 groups on the U.S. list of "foreign terrorist organizations," including al Qaeda and the Palestinian group Hamas. Designations need to be renewed every two years. The TTP is an alliance of factions and has killed many hundreds of people in bomb attacks in Pakistan. The five senators -- Charles Schumer, Frank Lautenberg, Kay Hagan, Kirsten Gillibrand and Robert Menendez -- said the group has committed atrocities aimed at nongovernmental organization workers, government officials and civilians. Putting the group on the list would help curtail support for its activities and pressure others to stop logistical, financial and political support for it, the senators said. U.S. officials in recent days have praised Pakistani efforts against militants, but Mrs. Clinton raised eyebrows over the weekend when she told the CBS television network that Pakistan would face "severe consequences" if a successful attack in the United States were traced to Pakistan. Since then, U.S. officials have sought to play down Clinton's comments. Richard Holbrooke, the U.S. special representative for Afghanistan and Pakistan, told reporters that Clinton's comments had been "not fully understood." "I am not here to criticize the (Pakistani) government but to thank it for what it has done," Holbrooke said late on Monday.