The UN special envoy to Yemen praised efforts to implement the historic Stockholm deal as he landed in Riyadh on Tuesday.

Martin Griffiths brokered the agreement between Yemen’s internationally recognised government and the Houthi rebels a year ago in Sweden.

The deal includes a ceasefire, a troop withdrawal in the port city of Hodeidah, the opening of a humanitarian corridor and a prisoner swap between the rebels and government.

But efforts towards putting the agreement into action stalled over the last 12 months due to a lack of trust between the sides.

“What I believe is happening now in Yemen is that at last ... we're beginning to see that shift take place,” Mr Griffiths told UN News.

“We're beginning to see in the hearts and minds of those who make decisions about the war, the desire to make peace and the recognition at a fundamental level that there is no prospect for military advantage; that there is nothing to be won on the battlefield, and that there is a huge victory, of course, to be made in the terrain of negotiation.”

The envoy met Houthi representatives in Sanaa, the Yemeni capital, on Tuesday before travelling to Saudi Arabia.

The deal reached in Sweden last year is regarded as a crucial confidence-building measure to help Yemen’s warring sides negotiate a political settlement to end the country’s devastating war. The meeting was the first for Yemen’s warring sides since peace talks faltered in Kuwait in 2016.

It was also the first time since the start of the conflict that they could come to an agreement on several important issues to alleviate the humanitarian situation in Yemen.

“Yes, certainly, there have been achievements,” Mr Griffiths said.

“People's lives have been saved, the humanitarian programme has been protected and I think it also showed that the parties could actually agree on a different way out of a crisis.”

But he expressed concern about the lack of progress on the prisoner exchange deal, a pivotal element of the overall agreement.

The exchange deal stalled as the two sides struggled to agree on its implementation during talks in Amman earlier this year. The talks verified the names of around 15,000 prisoners to be exchanged by both sides but thousands of detainees remain in the hands of the rebels.

“Many people, and I'm one of them, believe we could have done a much better job of implementing the Stockholm Agreement in these 12 months. And it has been for many of us, but particularly for the people in Yemen for whom it's a primary issue, a disappointment in many, many ways,” Mr Griffiths said.

The implementation of the Hodeidah deal has yet to be carried out and is at a standstill.

The Stockholm pact stipulated that Houthi forces leave three ports, including Hodeidah's, and that international monitors be sent to the region.

The monitors would then oversee a complete withdrawal of both sides' troops from the city, which would be run by “local authorities” under UN supervision.

Under the deal, both sides were to withdraw their troops by early January, but the agreement did not spell out who would control Hodeidah city after the rebel withdrawal.

"Negotiations are still ongoing over redeployments to demilitarise Hodeidah,” Mr Griffiths said. “We came out of the Sweden talks very buoyed by the fact that, for the first time ever, the two parties had made a voluntary agreement between themselves. So, we were very pleased about that."

What the negotiations in the Swedish capital showed was that there are many issues to resolve, he said.

“What it really taught me very, very strongly was that there are certain issues which will not be resolved by agreements at the sub-national level; specific agreements on different places,” he said.

“We have to address the fundamental issues of sovereignty, of legitimacy, through an agreement to end the war.”

The next step towards the implementation of the deal would be another round of talks, which can be expected sometime next year, a Yemeni government official told The National.

“We are hoping and pushing for a breakthrough,” the official said.