Yemen's warring sides have failed to reach an agreement on swapping thousands of prisoners of war, with both sides accusing each other of lying.
Negotiations between the Yemeni government and Houthi rebel representatives broke down in Jordan's capital, Amman, with the Yemeni government accusing the Houthis of providing a fake list of prisoners.
The deal to free prisoners was part of a series of confidence-building measures agreed to last month in Sweden that included a plan for the Houthis to withdraw from the contested port city of Hodeidah, a lifeline for millions of Yemenis facing famine, and place it under the control of an interim entity.
The two sides had exchanged the names of some 16,000 prisoners of war, and representatives from both the Yemeni government and Houthis rebels had said they expected the transfers to commence by January 19.
"They provided lists of names that were fake," Majid Fada'el, the Yemeni government's deputy minister for human rights told reporters.
"We don't even know where they got them from. On the other hand, we have reports and documents on those they have imprisoned. They said some of the names we provided were jailed on criminal charges or even belong to al-Qaeda but it's all lies. Sadly, the Houthis lie with every breath".
The Houthis, in turn, accused the Yemeni government of withholding information about prisoners being held by the government's allies, Saudi Arabia and the UAE.
Abdul Qader al-Murtada, a member of the Houthi delegation, said the rebels needed "more time".
"Those imprisoned in Saudi and UAE jails are still unknown. We only know of 300 names," he said.
"This means we need more time in order to identify them, to better deal with this humanitarian crisis".
Another round of talks planned
On Thursday, Murtada said the two sides had agreed to hold another round of talks to resolve issues that were holding back the implemention of the deal.
He did not specify when or where they could take place.
The United Nations Special Envoy for Yemen, Martin Griffiths, tried to appear upbeat and said the Amman meetings witnessed "positive" discussions.
"The meetings witnessed positive, constructive and frank discussions. The two parties took the first step in implementing the agreement by exchanging the lists of prisoners and detainees and providing responses on the exchanged lists".
The four-year war in Yemen has unleashed the world's most urgent humanitarian crisis with more than 22 million people needing some kind of aid to survive.
The conflict erupted in 2014 when the rebels stormed south from their stronghold of Saada and overran much of the country, including the capital Sanaa where they overthrew the government of President Abd-Rabbu Mansour Hadi.
The situation escalated in 2015 when Saudi Arabia and the UAE, who accuse the Houthis of being Iranian proxies, formed a coalition that launched a massive air campaign aimed at reinstating Hadi's government.
With logistical support from the US, the coalition has carried out more than 18,000 raids on Houthi-held areas in an attempt to reverse their gains.
According to recent estimates, as many as 85,000 children may have died from hunger since the coalition's intervention.