President Barack Obama says he would order another covert military raid like that which killed Osama bin Laden if it was necessary to stop terrorist attacks.
Pakistan is furious that that United States sent Navy Seals to raid bin Laden's Pakistan hideaway earlier this month without informing Pakistani authorities.
"We are very respectful of the sovereignty of Pakistan," President Obama. "But we cannot allow someone who is actively planning to kill our people or our - our allies' people - we can't allow those kind of active plans to come to fruition without us taking some action."
He said he could not allow "active plans to come to fruition without us taking some action," and would send troops again if a senior Taliban leader was found in Pakistan.
Mr Obama said that he had always made clear that he would take a clear shot at Bin Laden if one came clear.
Pakistan authorities were investigating how Bin Laden was able to stay in Pakistan without being detected for many years. President Obama said the al qaeda leader must have had an external support network outside the compound but that he did not have a definitive answer on the extent of official involvement in providing a safe haven in Pakistan.