WASHINGTON, Oct. 23 (Xinhua) -- U.S. President Barack Obama and visiting Pakistani Prime Minister Nawaz Sharif on Wednesday vowed to strengthen the two countries' security and economic cooperation during their first meeting, despite Islamabad's complains about U. S. drone attacks.

It was Sharif's first meeting with Obama since he won election in May, and the first official visit to Washington by a Pakistani prime minister in five years of tensions, which escalated in particular following U.S. killing of al-Qaida mastermind Osama bin Laden in a 2011 raid.

The two-hour meeting covered a broad range of domestic and regional issues, including counterterrorism cooperation, peace and security, collaboration on Pakistan's energy sector, increasing bilateral trade and investment, and the Afghanistan transitions.

After the meeting, Obama told reporters that the United States considers Pakistan as "a very important strategic partner."

Obama said the two spent a lot of time talking about economy and they also talked about security and their concerns about " senseless violence, terrorism and extremism."

He said they agreed to continue to find "constructive way" of partnership, both respecting Pakistan's sovereignty and concerns of both countries.

"It's a challenge. It's not easy," Obama acknowledged. "And we are committed to working together and making sure that rather than this being a source of tension between our two countries, that it can be a source of strength for us, working together in a constructive and a respectful way."

Sharif said the two had "a most cordial and comprehensive exchange of views" on bilateral and regional issues, in which he laid out his government's domestic focus in economy, energy, education and combating extremism.

"Pakistan and the United States have a strong ongoing counterterrorism cooperation. We have agreed to further strengthen this cooperation," said Sharif.

He noted in particular that he had brought up the issue of drones in their meeting, emphasizing the need for an end to such strikes.

The two leaders had a telephone conversation in May, in which Obama congratulated Sharif's election victory and they pledged to strengthen security cooperation.

During the four-day visit to Washington, Sharif also held talks with U.S. Secretary of State John Kerry on Sunday and had a breakfast with Vice President Joe Biden on Wednesday.

Although without any major breakthrough in sight, Obama and Sharif's first meeting in the White House were widely deemed as an sign of progress between the two countries following years of suspicion over Afghanistan and the U.S. counterterrorism fight.

Sharif's visit also came amid reports that the Obama administration has requested Congress to resume the military assistance to Pakistan of more than 300 million U.S. dollars.

Military assistance was frozen in 2011 after a U.S. operation killed bin Laden in Pakistan without Islamabad's knowledge, and a U.S. cross-border airstrike that killed a number of Pakistani soldiers.