Pakistan stood firm Thursday in charging that US-led forces deliberately carried out air strikes that killed 24 soldiers and led Islamabad to shut critical NATO supply routes to Afghanistan.

Pakistan's embassy in Washington invited reporters to a briefing at which officials showed images and maps that they said supported Islamabad's case, despite US insistence that the November 26 incident was a regrettable mistake.

An embassy official said that NATO forces could not have mistaken the two border posts on the Afghan border for bases of Islamic extremists such as the Taliban as they stood on high ground and had structures.

"It's in plain view on the top of a barren ridge, a place that terrorists perhaps would not be inclined to use as a hideout," said the official, who requested that his name not be used.

The Pakistani official declined to speculate on US motivations for an alleged deliberate attack.

"It's something which just doesn't make any sense to me given the kind of coordination mechanism we have, the kind of information-sharing we have, given the fact that these locations are mutually known to both sides," he said.

The incident comes amid high tension between the United States and Pakistan, whose military -- long the country's most powerful institution -- has been on the defensive since the secret US raid in May that killed Osama bin Laden.

President Barack Obama has voiced regret over the November 26 incident and said it was not deliberate. But Pakistan has been pushing for a full-fledged apology before it will consider reopening NATO supply routes into Afghanistan.

US officials say they are investigating the air strikes but have suggested that Pakistan gave the go-ahead for the air strikes after NATO forwarded coordinates of the targets.

The embassy official acknowledged that Pakistan received coordinates but said that they were incorrect and covered an area some 15 kilometers (nine miles) to the north of the incident.

According to the official's account, Pakistan's chain of command was reviewing the coordinates but NATO helicopters went ahead and started to strike a Pakistani border post shortly after midnight.

Communications with the first station went down and a second Pakistani post nearby opened 12.7-mm anti-aircraft fire on the NATO helicopters, which then proceeded to strike the second site, according to the official.

Islamic extremist groups effectively control parts of lawless northwestern Pakistan. US lawmakers are pushing through a bill that would freeze $700 million in aid to Pakistan amid growing US frustration with its war partner.