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 to reporters from his Downing Street office, Sunak said he would not outline the exact operational details of the plan, but said the government had made detailed 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."