In a blunt message to Pakistan, United States Secretary of State Hillary Clinton has said that the US will never tolerate a safe haven for those who kill Americans and it wants Islamabad to take concrete action in the war against terrorism.

"The United States has clear expectations for this relationship. And as President (Barack) Obama said on Wednesday night, US will never tolerate a safe haven for those who kill Americans," Clinton said on Thursday in her testimony before the powerful Senate Foreign Relations Committee.

"We are looking to Pakistan to take concrete actions on the goals we share: defeating violent extremism, which has also taken so many innocent Pakistani lives; ending the conflict in Afghanistan and securing a stable, democratic, prosperous future," Clinton said.