Pakistani President Asif Ali Zardari invited to NATO Chicago summit amid Afghan supply route talks

Updated at 2:19 p.m. ET

(AP) ISLAMABAD - 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 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 by making it clear Islamabad would not be welcome at the two-day summit beginning Sunday in Chicago unless it did so.

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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, which he said was not linked to any reopening of the supply lines.

The invite came hours ahead of a meeting in Pakistan of civilian and military leaders to discuss the supply line blockade. A lawmaker said participants would consider reopening the routes. Their recommendations would be sent to the Cabinet, which will meet on Wednesday to formally approve the decision, he said on condition of anonymity to discuss the sensitive matter.

A NATO diplomat in Brussels, also speaking condition of anonymity for the same reason, said the invitation to Zardari was meant as an inducement to the Pakistani government to reopen the borders.

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 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. 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 Qaeda on the defensive.

Pakistani Foreign Minister Hina Rabbani Khar said Monday that Islamabad had made the right decision to close the border, but strongly suggested that it was time to reopen it, saying that Pakistan couldn't afford to alienate the world for much longer.

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.

In Kabul, Afghanistan's deputy foreign minister Jawed Ludin said there are "some positive signs from Pakistan."

"It may be resolved today or tomorrow, but as it stands, it's still unresolved," Ludin told reporters on Tuesday.