Imran Khan, the cricketer turned politician, claimed he was taken off an international flight by US immigration officials and questioned about his views on drones and jihad before being allowed into the country, it emerged on Saturday
Mr Khan has emerged as a leading critic of US policy in Pakistan and Afghanistan, and his party is poised to make a breakthrough in elections due next year.
In a series of messages on Twitter, he described being stopped by US officials in Toronto on Friday.
"I was taken off from plane and interrogated by US Immigration in Canada on my views on drones. My stance is known. Drone attacks must stop," he wrote, adding that the delay caused him to miss his flight and a fund raising event in New York.
His anti-drone stance and his push for peace talks with insurgents in Afghanistan and Pakistan has led to accusations that he is sympathetic to Islamic extremists and earned him the nickname Taliban Khan.
Writing in The Daily Telegraph on Saturday, he dismissed such accusations and warned that Pakistan faced a never ending war unless the country's leaders engaged with the militant groups "Unless we address these very different groups and understand their motivation, senseless military operations will push all of them together, create yet more collateral damage and increase terrorism in Pakistan," he said.
Earlier this month he led thousands of supporters in a peace convoy demanding an end to drone strikes, which he says kill thousands of innocent people and radicalise scores of young men.
A spokeswoman for the US State Department confirmed the incident.
"We are aware that Imran Khan was briefly delayed in Toronto before boarding the next flight to the United States," she told Pakistani media. "The issue was resolved. Mr Khan is welcome in the United States."
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