Gilani said in a televised address, quoted Reuters, "Decisive steps have to be taken."
"In order to restore honor and dignity of our homeland and to protect the people, the armed forces have been called in to eliminate the militants and terrorists."
President Asif Ali Zardari expressed a commitment to defeating al-Qaida and its allies during talks in Washington, D.C., with President Barack Obama and Afghan President Hamid Karzai.
Meanwhile, Pakistani security forces continued to attack Taliban positions in Swat, an area about 80 miles from the country's capital Islamabad. The military said Wednesday it has killed more than 80 militants in Swat and the neighboring Buner region, reported the Associated Press.
The restive Swat valley has become a test of Pakistan's resolve to fight a growing Taliban presence in the country.
Pakistani authorities agreed in February to a Taliban demand for the introduction of Islamic sharia law in the Swat valley, raising concern among U.S. officials.
U.S. Secretary of State Hillary Clinton accused Islamabad of abdicating to the Taliban, while Mr. Obama expressed grave concern about the "very fragile" government, according to Reuters.
The U.N. High Commissioner for Refugees expressed deep concern about the safety of people displaced by the fighting, while the International Committee of the Red Cross said a humanitarian crisis was intensifying.
Several thousand civilians in the area took advantage of an easing in the army curfew to pour through Swat's main town, Mingora, in search of safety. Some left on foot with whatever they could carry, according to the AP.
"We can't stay here when bombs are falling," said Mingora resident Mohammad Hayat Khan as he loaded his family of 14 onto a pick-up truck. He told Reuters there had been shelling near his home.
More than 500,000 are already displaced by fighting in Pakistan's volatile border region with Afghanistan.