ISLAMABAD: President Asif Ali Zardari announced Thursday that he will attend the upcoming Nato summit in Chicago, accepting an invitation that was given after the country indicated it plans to end its six-month blockade of supplies meant for coalition troops in Afghanistan.

President Zardari's office said he agreed to attend the summit after it was endorsed by the Cabinet.

Pakistan closed its Afghan border to Nato supplies in November in retaliation for American airstrikes that killed 24 Pakistani soldiers. The route remains closed, but Pakistan's Cabinet has authorised officials to conclude their negotiations with the US over reopening it.

The government is likely to face domestic backlash once the supplies resume, partly because the Obama administration refused to apologise for last year's attack and stop drone strikes in the country as demanded by Pakistan's parliament.

Religious leaders on Thursday threatened to block the supply route if it does reopen, but it's unclear how successful they would be.

The US and Pakistan raced Wednesday to conclude a new agreement on the supply route, but the two sides remained at odds over how much money Islamabad should be paid to end the blockade. Pakistan has demanded higher fees for goods shipped through the country and has also clashed with the US over how much military aid it is owed.

The US Embassy declined to comment on the status of the negotiations Thursday.

Before the November attack, the US and other Nato countries fighting in Afghanistan shipped about 30 per cent of their nonlethal supplies through Pakistan. Since then, supplies have taken a far more expensive route through eastern Europe and Asia.

Pakistan has insisted the invitation to the upcoming Nato summit delivered earlier this week was not conditional on the status of the supply line. But many analysts believe the invite was forthcoming only after Pakistan indicated it would reopen the route.

The summit will largely focus on the Afghan war, and President Zardari will deliver a speech to the countries that make up the fighting force there, his office said in a statement. He will be accompanied by Foreign Minister Hina Rabbani Khar and Foreign Secretary Jalil Abbas Jilani.

Pakistan's presence at the meeting is seen as important because the country is considered vital to brokering a peace deal with the Taliban and their allies in Afghanistan that would allow foreign troops to withdraw without the country descending into further chaos.

Cooperation with Pakistan has been hampered over the last 18 months by steadily deteriorating relations with the United States. The downward slide began last January when a CIA contractor shot and killed two Pakistanis in Lahore who he said were trying to rob him. This was followed by the secret US raid last May that killed Osama bin Laden in Abbottabad, an operation that was seen as a gross violation of Pakistan's sovereignty.

Relations hit their lowest level after the US attack on two Afghan border posts in November that killed 24 Pakistani soldiers. The US claimed it was an accident, but the Pakistani army has said it was deliberate.

The US has expressed its regret for the incident, but has stopped short of offering the full apology demanded by Pakistan.

The refusal to offer an apology has outraged Pakistanis.

Amirul Azeem, a senior leader of Pakistan's largest religious party, Jamaat-i-Islami, said Thursday that the group's supporters would block Nato supplies because of Washington's refusal to honour parliament's demands.

''We will soon launch a movement to occupy Nato supply routes,'' said Azeem.