The Pentagon on Monday denied that US-led coalition helicopters based in Afghanistan were fired on in Pakistan and forced to turn back.
The incident "did not happen" said Pentagon spokesman Bryan Whitman, adding that after studying the facts, a statement by a Pakistani security official "didn't appear to be accurate."
Earlier there were conflicting reports that shots were fired when US-led coalition helicopters based in Afghanistan neared the border with Pakistan.
The gunfire was said to have broken out late on Sunday about 100 metres (yards) from the South Waziristan tribal area, where Al-Qaeda and Taliban fighters are believed to be sheltering. There were no casualties.
"The US-led coalition troops in helicopters came close to the border and they tried to sneak into Pakistan territory but shots were fired by Pakistani troops and the coalition troops retreated," a Pakistani security official said.
But Whitman said in Washington: "I can't find any mission that correlates to the reports I saw."
"I can't find any report about helicopters being fired upon," he added.
The incident was also denied by Pakistan army's chief military spokesman, Major General Athar Abbas. "These reports are not correct," he said.
"We have checked, there is an FC (Frontier Corps) post in the area. No helicopter came inside our side of the border, nor did our troops fire at any," Abbas added.
Islamabad has vowed to defend itself against violations of its air space and incursions by US forces in Afghanistan, after a series of missile strikes blamed on US-led coalition forces left 38 people dead in Pakistan.