The United States has asked Pakistan to prove its seriousness in fighting terrorism by matching their rhetoric with that of action on the ground than by mere "verbal commitment".

Special US Representative for Afghanistan and Pakistan Richard Holbrooke told the Pakistani leaders to prove that they were "serious" in the fight against terrorism, when he met on the sidelines of a meeting on Afghanistan at The Hague.

"I think there's almost no issue (commitment of Pakistan in taking action against terrorism) that's been as hotly debated as that one, and I have heard conflicting views," Holbrooke told the National Public Radio (NPR) on Tuesday.

"This morning, Secretary of State Hillary Clinton and I met with the foreign minister of Pakistan, (Makhdoom Shah Mahmood) Qureshi, and with the head of ISI, the Pakistani intelligence services, General (Ahmed Shuja) Pasha, and we went right to the heart it," he added.

General Pasha and Minister Qureshi said, we know that some people don't think we're serious, but we are serious. That's them speaking, Holbrooke said, adding "and our response was, well, the proof is in the pudding. We need to work together for practical results. Holbrooke said the attack on policy academy in Lahore came up prominently during the meeting with the Pak Foreign Minister and ISI Chief.

"The Foreign Minister said this is an attack on our very essence. It's outrageous. We want to work with you to root this out. So there's a lot of concern, and I think it's growing, in Pakistan as the violence spreads out of the tribal areas and eastward into Swat and now even into Lahore," he said.