British Prime Minister Rishi Sunak said on Monday the first flight carrying asylum seekers to Rwanda would leave in 10-12 weeks, as he set out plans for for his flagship policy to tackle illegal migration.

Speaking at a press conference, Sunak said he would not outline the exact operational details of the plan, but said the government had made specific preparations.

"I can confirm that we've put an airfield on standby, booked commercial charter planes for specific slots, and we have 500 highly trained individuals ready to escort illegal migrants all the way to Rwanda with 300 more trained in the coming weeks," Sunak said.

"We are ready. Plans are in place. And these flights will go come what may."

Under the timeline Sunak set out, the first flight would leave in July.

Sunak also said he was "confident" that the plan complied with all of Britain's international obligations, responding to a question about its membership of the European Convention on Human Rights.

"If it ever comes to a choice between our national security — securing our borders — and membership of a foreign court, I'm, of course, always going to prioritise our national security," he said, referring to the European Court of Human Rights.