The White House says President Barack Obama still considers Pakistan a strong ally in the fight against extremist forces. Comments by Mr. Obama's press secretary, Robert Gibbs, came Monday as the United States and Pakistan continued to discuss the closure of a key border crossing and amid concern about attacks on NATO supply convoys.

At a White House news briefing, Gibbs was asked about the attacks on NATO fuel tanker trucks, four of which occurred since Pakistan closed the northwestern Khyber Pass Torkhum border crossing last week.

The attacks followed what NATO says was a self-defense hot-pursuit action by helicopters. NATO expressed regret over the deaths of three Pakistani soldiers; a joint investigation is continuing.