Fighting continues to rage in Yemen, as Houthi rebels battle Saudi-backed government forces for control of strategic mountains near the Red Sea, and the leader of the Iran-aligned group accused the United States of considering direct military involvement in the conflict.

The clashes on Monday come amid mounting regional tensions set off by the US and Israel’s war on Iran. They also follow a report by The New York Times that US President Donald Trump had ordered air attacks against the Houthis on Sunday, only to call them off at the last minute.

The renewed hostilities have killed at least 674 people and displaced more than 158,000, officials said.

According to Al Jazeera witnesses, the Houthis – who seized Yemen’s Red Sea coast this month, including the port of Mocha – are now battling to take the Kahboub Mountains in Taiz and Lahj provinces. Control of the strategic heights, which overlook the Bab al-Mandeb Strait and Mayyun Island in the Red Sea, would allow the Houthis to sever the coast from the remaining government-held south.

“Since the Houthis entered Mocha and seized control of the port and later took Mayyun Island, they have been trying to advance into the mountains or make gains that would allow them to secure their rear,” said Al Jazeera’s Maha Ali, reporting from Taiz.

“Kahboub is now the main battlefield. It may remain so in the coming days given the mountain’s strategic importance and its oversight of Mayyun Island,” she said.

Trump reportedly calls off strikes

The fighting come amid media reports that Saudi Arabia’s Crown Prince Mohammed bin Salman has repeatedly pressed the US to join the fight. The Houthis on Saturday claimed an attack on the Saudi capital, Riyadh, for the first time since the recent escalation.

But Washington has so far rebuffed the requests, according to the reports.

The New York Times said on Monday that the Trump administration had prepared to launch air attacks on Sunday against the Houthis after fresh pleas from Riyadh. But it said Trump called off the attacks at the last minute, even as troops were loading bombs onto aircraft.

Houthi leader Abdel-Malik al-Houthi also said in an address that the US was considering a joint escalation with Saudi Arabia against his forces.

“Regional circumstances have kept the US and Israel somewhat preoccupied, creating a problem for the Saudi regime, which seeks their participation in its aggression and blockade against the Yemeni people,” the leader of the Iran-aligned group said. But he warned the US against escalation, saying the conflict will persist as long as Washington’s objective is “dominance over the Yemeni people”.

Analysts said Trump’s reported reversal underscored his administration’s reluctance to take on a new military commitment in a region where US forces were already stretched thin.

“President Trump was put in a very difficult position of whether to come to the aid of a world leader who he is trying to garner good relations with, but also whether to add another very difficult dimension militarily in a region where the US is already pretty bogged down,” said Jason Campbell, a senior fellow at the Middle East Institute.

The US military, he said, has already “expended a good amount of of higher end munitions” and a lot of the “interceptors need to be replenished”.

Toll rises

Yemeni government forces, meanwhile, said they struck Houthi fighters and supply lines near the Bab al-Mandeb Strait and in al-Bayda governorate, and shot down a Houthi drone in southwestern Taiz.

Major-General Abdulaziz al-Majidi, chief of staff of the Taiz military force, also told the state-run Saba news agency that soldiers and allied tribal fighters “liberated a number of areas” on the outskirts of Taiz after battling Houthi ground forces. Al Jazeera could not verify the battlefield claims.

The Houthis said Saudi Arabia carried out at least 157 air attacks in the provinces of al-Jawf, Taiz, Saada and Marib on Monday, killing at least one civilian. Another attack in Mocha late on Monday killed six civilians, including two children and a woman, the Houthi-affiliated Al Masirah TV reported.

There was no immediate comment from Saudi Arabia.

As fighting intensified, the World Health Organization said 674 people had been killed and almost 3,000 injured since August 6, including 164 deaths and 516 injuries between September 13 and 18 alone.

More than 158,000 people have been displaced this month, according to Yemen’s Executive Unit for the Management of Displaced Persons Camps. It said roughly 23,550 families had fled their homes across eight governorates, including Aden, Hodeidah and Taiz.

The conflict is also driving hunger across Yemen, where more than 18 million people or roughly half of the country already face acute food insecurity.

Carl Skau, the acting executive director of the World Food Programme (WFP), said “tens of thousands” of people are arriving in “overstretched” camps “with nothing”. He noted that Yemen imports 90 percent of its food, so when ports or airports are not working, “that’s having an impact on food security”.

A spokesperson for UN Secretary-General Antonio Guterres warned that continued fighting risked further damage to Yemen and its people, and said the UN special envoy for Yemen, Hans Grundberg, remained in contact with all parties to the conflict.