Washington (CNN) -- Pakistan's government has formally disputed the findings of a U.S. investigation into a November airstrike that killed 24 Pakistanis, saying the bombardment went on long after it reported its troops were under fire.
In a letter to the U.S. Congress, Pakistan said its troops came under fire at well-identified border posts and that NATO commanders knew helicopter gunships were firing on Pakistani forces "within the first fifteen minutes" -- yet the attack continued for more than another hour.
"This attack was the most recent example of the losses Pakistan has suffered fighting alongside the United States to combat terrorism and extremism," the letter states. The strike has strained ties between Washington and a key ally in the region, and "an apology by the U.S. Department of Defense to the people of Pakistan would not be inappropriate," the letter states.
The Pentagon said last week that the incident began shortly after 11 p.m. on November 25, when a U.S. contingent came under fire near the Pakistani border in southeastern Afghanistan. Brig. Gen. Stephen Clark, who led an investigation into the incident, said a lack of trust between NATO and Pakistani forces led to critical missteps by both sides.
At one point, about an hour into the confrontation, Clark said the Pakistani military reported to the Americans that they were under attack. But when asked for their location, the Pakistanis didn't want to give their location up, arguing that the coalition forces must know where they were because they were firing at them, he said.
Meanwhile, allied forces who had the exact coordinates of where their troops were only gave the Pakistanis a general location of where they were, Clark said -- and because of an inaccurate map, the description the coalition forces gave was not accurate, he said.
But in its letter to Congress, Pakistan said the incident "has raised suspicions in the rank and file of the Pakistan Army that it was a premeditated attack and was conducted to undermine the sovereignty and stature of Pakistan." The Pakistanis say their border posts came under fire first, and that any claim to the contrary is "baseless."
The letter argues that "the complete NATO chain of command" knew allied gunships were attacking Pakistani forces by 1:15 a.m. on November 26, but kept pounding the Pakistanis until about 2:20.
"At this point NATO was knowingly attacking Pakistani soldiers," it states. NATO commanders were well aware of the Pakistani positions, it added.
Pakistan's response was sent to U.S. lawmakers via the lobbying firm of Locke Lord Strategies, which acts as an agent for the Pakistani government in Washington.
CNN's Barbara Starr contributed to this report.