Washington: Noting that Pakistan's spy agency ISI continues to co-operate with the dreaded Haqqani network and Taliban, US Senator John McCain has said that continuation of terrorist safe haven in that country would make it tough for America to succeed in the war against terrorism.

"We have to have a realization that the present sanctuary situation in Pakistan cannot continue. Otherwise, it places enormous burdens on our ability to succeed," McCain said.

McCain said continuation of terrorist sanctuary now in Pakistan with the Haqqani network, the ISI cooperation with other groups including Taliban, is a major problem in this war against terrorism.

"I believe we've made significant successes. Our prayers and thoughts go out to the families of those brave, brave, elite of our elite that have sacrificed," she said.

"But, at the same time, we're going to have to address this sanctuary situation, and we're going to have to address the problem that the President has created, and that is that out there, there is the perception Afghanistan and other parts of that part of the world that America is withdrawing that can't be good," McCain said.

"There is no doubt that we have had significant success, particularly in the Southern part of Afghanistan. The reason why I worry a lot is I'm not sure we have a sufficient number of troops for another fighting season so we can gain control in the Eastern side of the country," he said.