United States President Barack Obama has urged that Pakistan must keep its commitments to root out the cancer of violent extremism. Obama said, his country will never tolerate a safe haven for those who aim to kill Americans. In a televised speech on troop withdrawal plans from Afghanistan, the US President said referring to Pakistan that, no country is more endangered by the presence of violent extremists. He said America will work with the Pakistan government to root out extremism. The US President sent a message that the US was ready to launch more direct assaults on safe havens harbouring terrorists who wanted to target Americans. Obama said, those who aim to kill Americans cannot elude, nor escape the justice they deserve. Obama's comments came in the midst of festering strains in ties between the US and Pakistan following the unilateral American action that killed al Qaeda chief Osama bin Laden in his hideout in Abbottabad, near Islamabad, last month. Obama made it clear that Washington will continue to press Islamabad to expand its participation in securing a more peaceful future for the war-torn region.