Pakistani officials say President Asif Ali Zardari will attend the upcoming NATO summit in Chicago, after Pakistan's cabinet endorsed a last-minute invitation to discuss the situation in Afghanistan.

NATO made the invitation to President Zardari earlier this week after Pakistan suggested it would soon re-open ground supply routes to international troops in Afghanistan.

Islamabad closed the supply routes to NATO nearly six months ago to protest U.S. airstrikes that mistakenly killed 24 Pakistani troops near the Afghan border.

Both sides are working to finalize a deal to end the blockade before the start of the NATO summit on Sunday. State Department spokesperson Victoria Nuland said Wednesday that some progress has been made in the negotiations.

“We've said from the very beginning that if we can get it done by Chicago, that will send a powerful signal of support from Pakistan to Afghanistan and to the larger support for the ISAF mission. That said, it's not done until it's done.”

On Monday, Pakistan's prime minister, Yousuf Raza Gilani, said his government was in serious discussions with U.S. officials on reopening the supply routes.

Until the talk of reopening the supply lines, it had been unclear if Pakistan – not a NATO member – would participate in the talks that will largely focus on the international community's commitment to Afghanistan's future.

Pakistani officials demanded an unconditional apology for the deadly NATO airstrikes. But Washington only offered condolences and Islamabad retaliated by cutting off NATO ground supply routes. The U.S. withdrew as much as $3 billion of promised military aid, as relations with Pakistan deteriorated.

The attack also prompted Pakistan's parliament to review its future engagement with the United States, with lawmakers calling for an end to U.S. drone strikes on Pakistani soil. Washington says the strikes targeting militants in Pakistan's northwest are crucial to defeating al-Qaida and the Taliban.