NATO on Tuesday invited Pakistan's president to the upcoming Chicago summit on Afghanistan, the strongest sign yet that Islamabad is ready to reopen its western border to U.S. and NATO military supplies heading to the war in the neighboring country.

Pakistan blocked the routes in November after American airstrikes killed 24 of its troops on the Afghan border. The attack sent ties between Washington and Islamabad to new lows, threatening regional cooperation needed for negotiating an end to the Afghan war.

The developments signal something of a rapprochement between the two countries, but tensions are likely to bedevil what has long been a brittle relationship, scarred by mistrust on both sides. Many in Washington believe Pakistan is supporting the Taliban, making the Afghan War unwinnable.

The U.S. expressed regret for the airstrikes and has been quietly pressing Pakistan to reopen the routes over the last two weeks. Washington and NATO stepped up those efforts in recent days, and officials had said Islamabad would not be welcome at the two-day summit beginning Sunday in Chicago unless it did so.

NATO Secretary-General Anders Fogh Rasmussen phoned President Asif Ali Zardari on Tuesday afternoon to invite him to the meeting, according to a statement from the Pakistan government and NATO.

"This meeting will underline the strong commitment of the international community to the people of Afghanistan and to its future," NATO spokeswoman Oana Lungescu said in Brussels, where the alliance is based. "Pakistan has an important role to play in that future."

In Islamabad, Zardari's spokesman Farhatullah Babar said the president would consider the invitation.

Pakistani civilian and military leaders later met to discuss the possibility of lifting the supply line blockade. In a statement, the Cabinet's defense committee endorsed the invitation to Chicago, suggesting that Zardari would accept it.

It stopped short of saying the supply routes would be immediately reopened but said that talks with the U.S. and NATO over the resumption should be "concluded." The full Cabinet is scheduled to meet on Wednesday to discuss the issue.

State Department spokeswoman Victoria Nuland was cautious, saying U.S. and Pakistani officials were still negotiating in Islamabad on reopening NATO supply routes. She said a deal before next week's NATO summit would be a "wonderful signal," but that the alliance decided that Pakistan should participate regardless of whether an agreement is finalized.

Pentagon spokesman George Little said the U.S. was hopeful that "in the very near future" the lines would reopen.

Pakistan sought to use the deadly American air strikes in November to extract new terms from the United States in what has always been a tense and largely transactional relationship. Noone expected the blockade to be permanent, so the main question became what concessions Islamabad could receive for reopening them.

The government has said it wants more money from the U.S. and NATO for hosting the supply routes, something Washington has indicated it could do.

The country's parliament also demanded an apology from Washington for the border incident and an end to America's drone strike campaign against militants in northwestern Pakistan, but neither appears likely, U.S. officials say. Negotiators from both countries have been discussing the drone strikes, which are unpopular in Pakistan, but Washington has said it will not stop them because they are vital to keeping al-Qaida on the defensive.

The defense committee only said the country "would remain engaged" with the United States on the question of an apology and the cessation of drone attacks.

By maintaining the blockade, Pakistan's teetering economy risked missing out on millions of dollars in international development and loans, as well military aid. It was also facing the prospect of being left out of discussions on the future of Afghanistan.

The blockade forced NATO to reorient its logistics chain to more expensive routes across Russia and Central Asia. While the war effort has not suffered, the Pakistani routes will be more important in coming months as NATO begins to pull out of Afghanistan, with a 2014 deadline for the withdrawal of all foreign combat troops.

Pakistan has some bargaining power of its own because its cooperation is seen as important to striking a peace deal with the Taliban and their allies in Afghanistan that would allow foreign troops to withdraw without sending the nation into further chaos.

The weak government risks some backlash from nationalist and Islamist groups, as well as militants, by reopening the supply lines. But the powerful army, which has influence over much of the country's media and some of its most firebrand politicians and clerics, is likely to tamp down the outrage.

More than 50 heads of state will attend the meeting in Chicago, including President Barack Obama who will be speaking in his hometown.


Lekic reported from Brussels. Associated Press writers Deb Riechmann in Kabul, Munir Ahmed in Islamabad and Lolita Baldor in Washington contributed to this report.