Yemen’s government and its allies Saudi Arabia and the United Arab Emirates asked the UN Security Council on Thursday to turn up the pressure on Huthi rebels to uphold a ceasefire deal.

In a letter sent to the council, the three governments accused the Huthis of violating the ceasefire in the port city of Hodeida 970 times since it came into force on December 18.

They asked the council to “impress upon the Huthis, and their Iranian backers, that they will be held responsible if their continued failure to comply… leads to the collapse of the Stockholm agreement,” said the letter seen by AFP.

Yemen’s Saudi-backed government and the Huthis agreed to the ceasefire and a redeployment of forces from Hodeida during UN-brokered talks in Sweden last month.

But deadlines for the pullback of forces and a prisoner swap have slipped, fueling worries that the Stockholm agreement may be in jeopardy.