After the Houthis rejected the American initiative ... Guterres discusses with the Minister of Foreign Affairs of Oman efforts to stop the war and the National Army is advancing in Taiz and Hajjah.

The Secretary-General of the United Nations, António Guterres, made a phone call with the Omani Minister of Foreign Affairs, Badr bin Hamad Al-Busaidi, to discuss the conflict in Yemen, while violent battles continued between the Yemeni army and the Houthis in 3 Yemeni governorates.

The Omani Ministry of Foreign Affairs said that the two sides discussed efforts made to stop the war and military operations and resort to peaceful solutions between the parties to the conflict through direct dialogue, which allows the entry of humanitarian aid to the Yemeni people.

The ministry added that during the call, it was emphasized to support the efforts of the UN envoy and the efforts of the US administration to stop the war and revive political negotiations.

As she put it.

The call came hours after the Houthi group announced its rejection of the US envoy Timothy Lenderking's plan to stop the war in Yemen and the principles of the joint declaration, which was welcomed by Saudi Arabia and the Yemeni government.

"The proposal presented by the US envoy to Yemen, in which he presented a ceasefire plan, did not carry anything new, and it represents the Saudi and international vision," said Houthi spokesman Muhammad Abdul Salam.

Abdul Salam added - in statements carried by the Houthi-affiliated Al Masirah TV - that the American proposal is just cosmetic detours that lead to the return of the blockade, and that it is just a plot to put Yemen in a more dangerous stage than it is now, as he put it.

For his part, Yemeni government spokesman Rajeh Badi said, "The proposed American initiative is a general outline agreed by the government out of concern for peace in the country.

Badi indicated - in an interview with Al-Jazeera - that the basic idea in the initiative presented by the US envoy to Yemen is a ceasefire and political dialogue.

American initiative

A Yemeni source revealed to Al Jazeera the terms of the US envoy’s plan to stop the war in Yemen and the principles of the joint declaration.

The document of principles stipulates a comprehensive ceasefire, including stopping Saudi raids and Houthi drones, and also includes opening Sanaa airport, allowing fuel supplies to enter from the port of Hodeidah, and the return of consultations.

The source explained to Al-Jazeera that there is a disagreement between the Houthis and the US envoy regarding the mechanisms, details and conditions of the joint declaration of the ceasefire, stressing that the Houthis, in return, presented their vision to the US envoy on a comprehensive ceasefire in Yemen.

Lenderking revealed earlier on Friday that he had offered a few days ago a plan for a ceasefire in Yemen to the Houthis, and said that his country was waiting for a signal from them about it.

He added that Saudi Arabia "is ready to deal with the conflict in Yemen in a way it was not prepared to deal with 6 months ago, and it is determined to provide all support to the American efforts."

The US official said that he would return to the region "immediately when the Houthis are ready for dialogue," adding, "If we are unable to make progress now, the country will enter into conflict and greater instability."

Fierce battles

Despite diplomatic efforts, battles continue in the governorates of Taiz, Hajjah and Ma'rib. Local sources told Al-Jazeera that "the National Army forces have taken control of the Al-Zuhaib and Al-Arf mountains in the Maqabneh district, west of Taiz, after violent battles with the Houthis."

The sources added that the army forces aim to advance towards the strategic "Al-Barah" area, where the main road linking the city of Taiz and the coastal areas of the governorate is located.

As for Hajjah, in the west, Yemeni military sources report that the army launched a military operation that enabled it, after battles with the Houthis, to control areas and villages in this governorate.

The sources confirm that the Saudi-Emirati coalition aircraft provided air cover for the Yemeni army's attack, noting that the battles caused dozens of deaths and injuries on both sides.

In Marib, the coalition said it had "destroyed the Houthi air defense system."

The Saudi Press Agency stated that the destruction of the system included all its components, including foreign experts.

As she put it.

Since February 7, the Houthis have stepped up their attacks in the Marib Governorate to control it, as it is the most important stronghold of the Yemeni government and the main headquarters of the Ministry of Defense, in addition to its enjoyment of oil and gas wealth.

UN warnings

In a related context, a spokesman for the Secretary-General of the United Nations, Stephane Dujarric, said, "The humanitarian situation in Marib, Yemen is getting worse, as fighting continues on multiple fronts."

Dujarric confirmed - in an interview with Al Jazeera - that civilians are paying the highest price in this war.

He called for an immediate cessation of hostilities throughout the country, noting that the battles have forced 15,000 people to flee since early February, and nearly 60% of them are staying in random camps and crowded and underserved locations.

According to Doujarik, more than 20 million people need humanitarian aid, many of them on the brink of starvation.

"The improvement of the humanitarian situation in Yemen should not be dependent on the development of the political situation in Yemen," he said, calling on all relevant countries to work with the United Nations to end what he described as the humanitarian nightmare in Yemen.

Dujarric stressed that the international envoy to Yemen Martin Griffiths is working according to a clear and direct mandate from the UN Security Council, and that he does not represent any other party.

Yemen has been witnessing a war for more than 7 years, which has killed 233,000 people, and 80% of the population - about 30 million people - have become dependent on support and aid, in the worst humanitarian crisis in the world, according to the United Nations.

The conflict has had regional extensions since March 2015, as a coalition led by the Saudi neighbor has been carrying out military operations in support of government forces, in the face of the Iran-backed Houthis who control several provinces, including the capital, Sanaa.