Polish President Andrzej Duda has ruled out the possibility of his country delivering fighter jets to Ukraine without first agreeing the move with allies, as the question divides backers of Kyiv.

Such a decision would have to be taken jointly by NATO allies, Duda told the BBC, days before he is due to visit London. Duda said his country’s air force has fewer than 50 U.S.-made F-16 aircraft, which he says is not enough for Poland.

Ukrainian President Volodymyr Zelensky has repeatedly called for fighter jets to help fend off Russian attacks.