The Yemeni government and Houthi rebels accused each other of intransigence after the failure of month-long prisoner exchange talks, another humanitarian setback in the seven-year civil war. UN special envoy to Yemen Martin Griffiths said on Sunday that the talks to release 300 prisoners ended in Amman without results. The prisoners include senior government figures, journalists and academics. The diplomatic and military landscape has changed in favour of the Iran-aligned Houthis since the two sides exchanged more than 1,000 prisoners in November. The swap was the result of a deal made during an earlier round of talks in Montreux, Switzerland. Government delegates said a decision by US President Joe Biden to revoke a Houthi terrorism designation emboldened the group, which renewed an offensive this month on the ancient city of Marib. Majed Fadhil, one of the delegates, said the Houthi side declined to release half of 136 names presented by the government in a list that formed the basis for the talks. "They kept changing their positions. Their intransigence was clear," Mr Fadhil told <em>The National</em>. He said the Houthi advance on Marib made the group less serious about pursuing a prisoner swap. But Abdelkader Al Murtada, head of the Houthi delegation, said his side “tried every way to make the talks successful”. He said the Houthis proposed releasing all sick and wounded prisoners from both sides, as well Houthi and government prisoners captured in Marib province. “The talks ended without progress because of the intransigence of the aggressor powers,” he tweeted. Mr Griffiths had imposed a ban on speaking to the media on both sides during the talks, in a bid to contain tension. His office, as well as the International Committee for the Red Cross, supervised the talks. Addressing the UN Security Council on Thursday, Mr Griffiths said the Houthis must stop their attack on Marib. He described the attack as a “sharp escalatory turn”. Thousands of Yemenis are in jail or have vanished during the civil war, with the Marib battles raising the spectre of another wave of mass displacement. There has been a debate about who gets released during the talks, for example, there are worries that freeing Houthi prisoners will allow them to rejoin the battlefield fight in Marib, Elana Delozier, a Yemen expert at the Washington Institute for Near East Policy said. "The prisoner release talks have failed more than they have succeeded, and the last success was an anomaly the UN hoped would repeat itself. Instead it seems it wasn't in the cards this time," Ms Delozier told <em>The National.</em> About two-thirds of Yemen’s 21 million people receive handouts from international organisations. The UN says thousands of people are on the brink of famine. The main conflict in Yemen is between the internationally recognised Yemeni government and other forces in a Saudi-led coalition against the Houthis, who overran the capital Sanaa in 2014. Al Qaeda is also a powerful player in the country. Hadi Haig, another government delegate, said the Houthi side “had insisted on foiling the talks after the terror designation on it was lifted”. The Biden administration, which intends to return to the 2015 nuclear deal with Iran, withdrew military support in recent weeks for the Saudi Arabian-led intervention in Yemen. It lifted some sanctions on the Houthis and told Congress that it would remove the Houthis from a US list of terrorist organisations. The designation, and the sanctions, were made in the waning days of the Donald Trump administration. But US officials cautioned that these policy changes should not be interpreted as endorsement of Houthi offensive operations. The US state department said last week that the Houthis must halt the Marib attack, cease all military operations and end attacks on Saudi Arabia.