Yemeni officials say an informal agreement to reduce hostilities between Saudi-led coalition forces and rebels in and around the Red Sea port city of Hodeida has taken hold. He reported three wounded guards.
After failed peace talks in September, the United Nations is pushing to host a new round of negotiations between the Yemeni government alliance, led by Saudi Arabia and the UAE, and the country's Iran-linked Huthi rebels by the end of the year.
The Saudi-led coalition now "appears determined to take Hodeidah, which in my opinion will still not allow the real start of a political solution", Mr Guterres said. It also expressed concern over the safety of those trapped in Hodeida as the intensified military operations "are increasingly confining populations and cutting off exit routes".
"The Saudi-led coalition have agreed to the evacuation of wounded Houthis from Yemen, one of the key stumbling blocks to the UN Geneva talks in September", it added.
On the ground in Hodeida, a relative calm was holding for a second full day and despite the thundering sound of jets flying overhead, no major fighting was reported.
The slowdown in fighting follows diplomatic efforts to end the conflict in the city, whose port serves as a key lifeline to the impoverished country.
Pro-government forces have temporarily stopped their advance into the city to allow safe passage for civilians, humanitarian staff and wounded, a military official told AFP.
During the past few days, the government forces made significant progress in Hodeidah despite a large number of landmines and booby-trapped buildings, in addition to professional Houthi snipers who took positions on buildings inside residential neighborhoods, according to local military sources.
"The battles will not stop, except with the liberation of Hodeida and the whole west coast", he said.
"We are ready, and present, and our plans are in place" in case of an attack by the rival pro-government alliance, the spokesman said at a news conference broadcast on the rebels Al-Masirah TV, which did not give his name.
Three port employees reached by telephone said the rebels had also begun to mine entryways to the port overnight.
The Houthis had planted explosives near two of the port's gates, one that leads to Jizan Road, a main street in the city's north, and the other near the Alsanabel flour mill company, they said.
The deputy director of the port, Yehya Charafeddine, told AFP on Tuesday that the port's main entrance "had been the target of air raids [.] but the port is functioning normally".
The United States, Britain and France - three of the main arms suppliers to Saudi Arabia - have also called for an end to almost four years of conflict in Yemen, particularly in Hodeida.