US President Barack Obama's warning to Islamabad over suspected ties to militants will hurt efforts to stabilize Afghanistan and fuel anti-Americanism, the chairman of Pakistan's Senate Foreign Affairs Committee said on Friday.

Pakistan is seen as critical to bringing peace to neighboring Afghanistan, but the United States has failed to persuade it to go after militant groups it says cross the border to attack Western forces in Afghanistan.

"This is not helping either the United States, Afghanistan or Pakistan," Salim Saifullah told Reuters. "There will be pressure on the (Pakistan) government to get out of this war," he said, referring to the US war on militancy.

Obama warned Pakistan on Thursday that its ties with "unsavory characters" had put relations with the United States at risk, as he ratcheted up pressure on Islamabad to cut links with militants mounting attacks in Afghanistan.

He accused Pakistan's leaders of "hedging their bets" on Afghanistan's future, but stopped short of threatening to cut off US aid, despite calls from lawmakers for a tougher line over accusations that Pakistani intelligence supported strikes on US targets in Afghanistan.

Pakistan joined America's "war on terror" after the Sept 11, 2001, attacks on the United States. But its performance against militants is a frequent source of tension between Washington and Islamabad.

Ties were heavily strained after US special forces launched a unilateral raid that killed Osama bin Laden in a Pakistani town on May 2.

They deteriorated further after the top US military official accused Pakistan's Inter-Services Intelligence spy agency of supporting a Sept 13 attack by the Taliban-allied Haqqani militant group on the US embassy in Kabul.

Saifullah said Washington's public criticism of Pakistan was counter-productive and would only play into the hands of militant groups.

"War in Afghanistan is passing through a critical phase, evolutionary phase," he said. "At this stage, muddying water is not appropriate. This is exactly what the militants want. They are playing to their tune. This is adding strength to them."

The United States has long called for a military offensive against the Haqqani network, which it says is based in North Waziristan, a global hub for militants on the Afghan border.

Analysts say Pakistan sees the Haqqani network - perhaps the most feared Taliban-allied insurgent group in Afghanistan - as a counterweight to the growing influence of India there.