In a major blow for Rishi Sunak, Downing Street refused to say whether the agreement will be struck before Christmas.
The treaty is a key part of the government’s response to the Supreme Court’s unanimous ruling that the policy of deporting asylum seekers to Rwanda is unlawful.
Sunak said the treaty would address the court’s main complaint that the migrants could be deported from Rwanda back to their home countries.
Speaking on Sky News on November 16, the day after the court ruling, home secretary Cleverly said: “It is ready, pretty much now, to turn into a treaty that can be done within days - not weeks or months - days.”
But the prime minister’s spokesman this morning confirmed that would not now be happening.
He said: “We still plan to publish the treaty ... in the coming weeks.”
However, he refused to say whether that would be before the House of Commons rises for the Christmas recess on December 19.
The confirmation that the treaty, as well as emergency government legislation declaring Rwanda a safe country, may not be ready until next year risks further angering right-wing Tory MPs.
The Rwanda plan is a key element of Sunak's pledge to "stop the boats" carrying asylum seekers across the English Channel.
Cleverly's commitment to the policy has already come into question after he repeatedly refused to deny once calling it "batshit".
In an interview with The Times at the weekend, Cleverly also insisted the policy is "not the be all and end all" when it comes to the government's attempts to reduce immigration.