Rouhani heads to UN in bid to win Iran support against 'cruel' US

President Hassan Rouhani set off for New York on Monday to attend the UN General Assembly on a mission to win Iran support against "cruel" pressure from arch-foe the United States.

His departure came as Iran said an oil tanker flying the flag of US ally Britain was "free" to leave more than two months after its forces seized it in sensitive Gulf waters.

Speaking before boarding his flight, Rouhani said his delegation was heading to the UN gathering despite reluctance from President Donald Trump's administration to issue them visas.

Tehran and Washington have been at loggerheads since May last year when Trump abandoned a 2015 nuclear deal and subsequently began reimposing sanctions on Iran in a stated campaign of "maximum pressure".

"When the Americans aren't willing (to let Iran participate), we must insist on travelling," Rouhani said.

"It is essential for us to take part in the UN General Assembly and talk at various levels," he told a news conference at Tehran's Mehrabad ...