Seeking to improve a rocky relationship, President Barack Obama and Pakistani Prime Minister Nawaz Sharif on Wednesday pledged cooperation on the security issues that have strained ties between their nations. But the sources of the long-standing tensions did briefly bubble to the surface.

Speaking alongside Obama at the White House, Sharif said he raised the issue of American drone strikes during their two-hour meeting, ``emphasizing the need for an end to such strikes.'' For his part, Obama made no mention of drones, which have stoked widespread resentment in Pakistan where many believe the targeted strikes by the armed unmanned aircraft kill large numbers of civilians.

Despite the Pakistani concerns, the U.S. has shown no indication it is willing to abandon the attacks, even though the number has dropped in the past couple of years.

Wednesday marked the first time Obama and Sharif have met since the Pakistani leader took office in June. And the mere fact that the talks took place was seen as a sign of progress after a particularly sour period in relations between the security partners.

Obama acknowledged that there will always be some tension between the U.S. and Pakistan, but said he and Sharif agreed to build a relationship based on mutual respect.

``It's a challenge. It's not easy,'' he said. ``We committed to working together and making sure that rather than this being a source of tension between our two countries, it can be a source of strength.''

Washington has warmly welcomed Sharif, who arrived on Sunday for his first visit to the U.S. capital since taking office.

He dined with Secretary of State John Kerry and other top U.S. officials and was hosted at a breakfast meeting Wednesday at Vice President Joe Biden's residence.

Sharif's wife was also the guest of honor at a tea and poetry reception hosted by first lady Michelle Obama and Jill Biden, the vice president's wife.

A military honor guard also lined the driveway leading to the West Wing of the White House as Sharif arrived for his meeting with Obama.

Beyond drones, the other hot-button issues on the agenda for Wednesday's meeting included plans for winding down the U.S.-led war in Afghanistan and the longstanding tensions between India and Pakistan.

Both leaders agreed on the need for a stable and secure Afghanistan after combat missions formally conclude there at the end of next year.

Pakistan's conflict with India over the disputed region of Kashmir was also a central topic of the talks. Obama praised Sharif for seeking to end tensions between the two nuclear-armed neighbors.

``Billions of dollars have been spent on an arms race in response to these tensions,'' Obama said.

``Those resources could be much more properly invested in education, social welfare programs on both sides of the border between India and Pakistan.''

Sharif said he was committed to cooperation with India, including on Kashmir. The Pakistani leader also invited Obama to visit Pakistan, but the U.S. president did not publicly accept the offer.

During his first term, Obama had told Pakistani officials that he wanted to visit the country, but those plans were halted by the increased tensions that followed the bin Laden killing.