KARACHI, Pakistan (Reuters) - Thousands gathered outside the American consulate in the city of Karachi on Sunday to protest against a NATO cross-border air attack that killed 24 Pakistani troops and is threatening a strategic alliance between the countries.
A Reuters reporter at the scene said the angry crowd shouted "Down with America." One young man climbed on the wall surrounding the heavily fortified compound and attached a Pakistani flag to barbed wire.
The NATO attack was the latest perceived provocation by the United States, which infuriated Pakistan's powerful military with a unilateral U.S. special forces raid that killed al Qaeda leader Osama bin Laden in May.
"America is attacking our borders. The government should immediately break ties with it," said Naseema Baluch, a housewife attending the Karachi demonstration.
"America wants to occupy our country but we will not let it do that."
"This was a tragic unintended incident," NATO Secretary-General Anders Fogh Rasmussen said in a statement, adding that he fully supported a NATO investigation that was under way.
"We will determine what happened, and draw the right lessons."
That is unlikely to cool tempers. Many Pakistanis believe their army is fighting a war against militants that only serves Western interests and hurts their country.
"U.S. stabs Pakistan in the back, again," said a headline in the Daily Times, reflecting fury over the attack in Pakistan, a regional power seen as critical to U.S. efforts to stabilize neighboring Afghanistan.
Pakistan on Sunday buried the troops killed in the attack.
Television stations showed the coffins draped in green and white Pakistani flags in a prayer ceremony at the headquarters of the regional command in Peshawar attended by army chief General Ashfaq Kayani.
"This negates the progress made by the two countries on improving relations and forces Pakistan to revisit the terms of engagement," a Foreign Ministry statement quoted Khar as telling her U.S. counterpart.
Khar also informed Clinton that Pakistan wants the United States to vacate a drone aircraft base in the country.
Pakistan shut down NATO supply routes into Afghanistan -- used for sending in nearly half of the alliance's land shipments -- in retaliation for the worst such attack since Islamabad uneasily allied itself with Washington following the September 11, 2001, attacks on the United States.
About 500 members of Jamaat-e-Islami, Pakistan's most influential religious party, staged a protest in Mohmand tribal area, where the NATO attack took place.
"Jihad is The Only Answer to America," they yelled.
Pakistan is reviewing whether it will go ahead with plans to attend a major international conference in Bonn next month on the future of Afghanistan in light of the NATO attack.
Around 40 troops were stationed at the outposts at the time of the attack, military sources said.
"They without any reasons attacked on our post and killed soldiers asleep," said a senior Pakistani officer.
Pakistan responded with unusually strong condemnations and said it reserved the right to retaliate.
Pakistan is a vital land route for nearly half of NATO supplies shipped overland to its troops in Afghanistan. Land shipments account for about two thirds of the alliance's cargo into Afghanistan.
A similar incident on Sept 30, 2010, which killed two Pakistani service personnel, led to the closure of one of NATO's supply routes through Pakistan for 10 days.
U.S. ties with Pakistan have suffered several big setbacks starting with the unilateral U.S. special forces raid in May that killed bin Laden in a Pakistani town where he had apparently been living for years.
Pakistan condemned the secret operation as a flagrant violation of its sovereignty, while suspicions arose in Washington that members of Pakistan's military intelligence had harboured the al Qaeda leader.
The military came under unprecedented criticism from both Pakistanis who said it failed to protect the country and American officials who said bin Laden's presence was proof the country was an unreliable ally in the war on militancy.
Pakistan's army, one of the world's largest, may see the NATO incursion from Afghanistan as a chance to reassert itself, especially since the deaths of the soldiers are likely to unite generals and politicians, whose ties are normally uneasy.
"From Raymond Davis and his gun slinging in the streets of Lahore to the Osama bin Laden incident, and now to the firing on Pakistani soldiers on the volatile Pakistan-Afghan border, things hardly seem able to get any worse," said the Daily Times.
Islamabad depends on billions in U.S. aid and Washington believes Pakistan can help it bring about peace in Afghanistan ahead of a combat troop withdrawal at the end of 2014.
But it is constantly battling Anti-American sentiment over everything from U.S. drone aircraft strikes to Washington's calls for economic reforms.
"We should end our friendship with America. It's better to have animosity with America than friendship. It's nobody's friend," said laborer Sameer Baluch.
In Karachi, dozens of truck drivers who should have been transporting supplies to Afghanistan were idle.
Taj Malli braves the threat of Taliban attacks to deliver supplies to Afghanistan so that he can support his children. But he thinks it is time to block the route permanently in protest.
"Pakistan is more important than money. The government must stop all supplies to NATO so that they realize the importance of Pakistan," he said.
But some Pakistanis doubt their leaders have the resolve to challenge the United States.
"This government is cowardly. It will do nothing," said Peshawar shopkeeper Sabir Khan. "Similar attacks happened in the past, but what have they done?".