WASHINGTON (AP) — 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 in the Oval Office, 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.