The US ambassador to Yemen on Thursday directly criticised Iran-backed Houthi militias for stalling the implementation of a UN-brokered peace deal. Matthew Tueller said he was "greatly frustrated" by the Houthi actions to delay the withdrawal of all forces from the Red Sea city of Hodeidah and hand it over to civilian and UN management, as agreed in Sweden last December, but had not "given up hope". The US ambassador also said Houthi weapons posed a danger to the region and Yemen, and that the United States would not support groups seeking to divide Yemen. The UN-backed ceasefire, reached at the first talks between the warring parties in two years, was a major breakthrough that raised hopes of a political solution to a civil war that has triggered one of the world's worst humanitarian crises. But the Houthi rebels have failed to withdraw fully from Hodeidah, a strategically important port city. "We are willing to work with others in order to try to implement these [Sweden] agreements and see whether the Houthis can in fact demonstrate a political maturity and start to serve the interests of Yemen rather than acting on behalf of those who seek to weaken and destroy Yemen," Mr Tueller said during a televised news conference in Aden. The US ambassador’s comments came after a senior Houthi official said they refused to adhere to the agreement and would keep their forces deployed in Hodeidah. Mohammed Ali Al Houthi, head of the rebels' Supreme Revolutionary Committee and a cousin of the group’s leader, accused the government of misinterpreting the Swedish peace deal. He said the government “could not get the port by force and they will not seize it by tricks”. “We agreed on the redeployment according to the presented mechanism, but withdrawal, as they are promoting, is impossible,” Al Houthi said. Officials from Yemen's internationally recognised government said the Houthi refusal to give up Hodeidah would trigger further conflict in the city and exacerbate the humanitarian crisis. The international community fears renewed fighting in Hodeidah might jeopardise the peace agreement and disrupt transport of humanitarian aid to the rest of the country. Rageh Badi, government spokesman, said the rebels' refusal to adhere to the peace agreement and the Houthi official’s remarks were effectively a “declaration of war". He urged UN to increase pressure on the Houthis to prevent another "explosion of the situation" in Hodeidah. Renewed fighting is just a "few days" away if no actions are taken against the group, he said.