Trump was interviewed by phone on Thursday by Nigel Farage, leader of the Brexit party and rival of Johnson in the upcoming election on December 12.

The president said that a U.S.-U.K. trade deal would be impossible under the current terms of Brexit, which Johnson reached with the European Union.

“We want to do trade with the U.K. and they want to do trade with us. And to be honest with you, this deal, under certain aspects of the deal, you can’t do it,” Trump told Farage on his radio show on London station LBC, according to the Wall Street Journal. “You can’t trade. We can’t make a trade deal with the U.K.”

The British government, however, has said that under Johnson’s Brexit agreement, the U.K. would be removed from the EU’s customs area and it would be free of the EU’s regulations, allowing it to sign bilateral trade deals with the U.S. and other countries.

Trump’s appearance on Farage’s show sends a mixed political signal, as Trump and Johnson have typically been closely aligned. Johnson’s left-wing rival, Jeremy Corbyn, accused him in August of intending to lead the U.K. “straight into the arms” of Trump. Farage’s Brexit party criticizes Johnson from the right, calling for an abrupt split from the union rather than any sort of agreement.

On Thursday, Johnson on Twitter accused Trump of “ trying to interfere in UK election to get his friend Boris Johnson elected” after Trump said that Johnson would be “so bad” for Britain if elected.

Britain agreed Wednesday to hold a general election on Dec. 12 in an effort to shake up Parliament and break the months-long Brexit stalemate. The European Union has extended Britain’s Brexit deadline to Jan. 31.

Even so, Trump said Johnson is a “fantastic man” who is “exactly the right guy for the times.” He said he’d like to see an electoral pact between Johnson’s Conservatives and Farage’s Brexit Party, saying the two together would be an “unstoppable force.” Neither party has indicated such a deal is on the table.

“Absolutely not and indeed as I say the High Court in England plainly agrees with us but the Supreme Court has to decide,” he told the BBC, when asked if he lied to her when he gave his reasons to suspend Parliament.

The queen suspended Parliament this week until a Queen’s Speech on Oct. 14. She did so on the advice of Johnson. While it is a standard move in parliamentary procedure, it is controversial as well, with the U.K.’s Oct. 31 deadline for leaving the E.U. looming large.

Johnson, however, advised the queen that it was because his government needs to launch a new domestic agenda starting next month. It is a generally accepted rule that the monarch should not be forced to take a side in a political debate wherever possible, and doing so is seen as a significant breach of parliamentary protocol.

The English High Court said that decision was not one for the courts, but Scotland’s highest court ruled Wednesday that it was illegal “because it had the purpose of stymieing Parliament.”

However on Thursday an Irish court rejected the claim that it was illegal because it risked undermining the Northern Irish peace process. As Johnson said, it now goes to the country’s Supreme Court for a final call.

Johnson replaced Prime Minister Theresa May by promising to get Britain out of the E.U. with or without a formal withdrawal agreement by the deadline. But last week Parliament passed a bill ordering him to seek a Brexit delay if there is no deal formed.

Johnson responded by calling for a general election, but that did not get enough votes to be formally called. The opposition does not want an election until after a delay has been achieved. It is not yet clear if Johnson will seek that delay as Parliament has instructed.

The government was also forced by lawmakers to release the government’s assessment of the fallout from a no-deal Brexit. The document, “Operation Yellowhammer” predicts huge delays at ports and possible food and medicine shortages. The government has downplayed those predictions, saying they were made before the government started accelerating preparations.

Johnson faces a significant anti-Brexit bloc in Parliament, as well as pressure from the right in the form of the Brexit Party.

While leader Nigel Farage has offered Johnson an electoral pact if he sticks with a no-deal Brexit, he could also prove to be a thorn in Johnson’s side if the government delays the departure further and pro-Brexit Tories defect to the Brexit Party in any future election.