Saudi and Yemeni forces pressed a counteroffensive against Houthi fighters Monday, officials said, seeking to oust the rebels from the strategic port city of Mokha and ease the threat to energy exports though the narrow Bab al-Mandeb strait.

Around 100 jet fighters were providing air cover to Yemeni ground troops as they pushed north along the coast in a flanking move toward Mokha in a dawn operation, said Maj. Gen. Turki al-Maliki, a spokesman for the Saudi-led military coalition in Yemen.

Since taking the city last month, the Houthis have attacked Saudi energy facilities and threatened Saudi ship traffic through the 18-mile wide entrance to the Red Sea, raising concerns from Riyadh, Europe and Washington about further disruptions in the oil supply from the region.

"We executed a flanking operation to gain control over the Bab al-Mandeb Strait," said Col. Majid al-Nuzaili, a Yemeni military spokesman, in a social-media post. He said the operation included Emirati-backed pro-government forces known as the Giants Brigades and had succeeded in gaining control over the strait, but that couldn't be separately confirmed.

The escalating fighting in Yemen, the worst in the country in years, shows how the war in Iran is fueling instability throughout the Middle East and heightening the risk to global energy flows after Tehran's closure of the Strait of Hormuz in March caused the worst oil-supply jolt in recent history.

Secretary of State Marco Rubio told reporters on Monday: "The Saudis have come under Houthi attack and see the threat that that poses, and they have a right to defend themselves. And obviously the Yemeni forces are going to try to retake territory that they were ousted from."

The Houthis seized Mokha early last month, expanding their territory closer to the narrowest parts of the Bab al-Mandeb strait and threatening Saudi oil exports. They are likely to respond to the latest offensive with new attacks on Saudi Arabia, including on its energy infrastructure, analysts said.

"The Houthis are definitely going to escalate," said Adam Baron, a fellow at the New America Foundation in Washington who specializes in Yemen and the Persian Gulf. "They want to push back against their losses by striking Saudi to show they still have the capacity to disrupt the kingdom's economy."

Saudi Crown Prince Mohammed bin Salman last month asked President Trump for military help against the Houthis, but Trump has limited U.S. involvement to providing intelligence and other indirect support, according to a U.S. military official.

For the U.S., opening another active military front against the Houthis risks overextending U.S. forces and deepening the risks to international shipping, analysts said. The Houthis have largely avoided targeting American or international commercial ships in the region following a 2025 ceasefire with the U.S.

The U.S. has also become more confident that its naval blockade of Hormuz is having a severe effect on the Iranian economy. U.S. and Gulf officials said Iran was losing control of the Strait of Hormuz, with millions of barrels of oil passing through an essential waterway for crude-oil transit and the global economy.

The Houthis are among an array of militia groups throughout the Middle East that receive weapons and training from Iran and its Islamic Revolutionary Guard Corps as a part of Tehran's strategy to project power in the region. But they had remained largely on the sidelines of the war between the U.S. and Iran until a ceasefire in Yemen unraveled in July.

The Saudi-backed ground operation is relying on Yemeni fighting units that Saudi Arabia and the United Arab Emirates armed and trained at earlier stages of the civil war when the conflict ground to a bloody stalemate.

The war began in 2014, when the Houthis swept into San'a. A Saudi-led coalition entered the war on behalf of Yemen's internationally recognized government in 2015. The conflict has killed more than 150,000 people, displaced millions and pushed the Arab world's poorest nation to the brink of famine.

In recent years, a tentative ceasefire had held as Saudi Arabia paid the salaries of Yemeni government officials, including those in San'a. That came as the Houthis attacked Israel and struck ships in the Red Sea during the Israel-Hamas war in the Gaza Strip.

When the Houthis began their new offensive in early September, they quickly swept into the Red Sea port city of Mokha and took Perim Island in the Bab al-Mandeb, the narrow southern mouth of the Red Sea. That gave the Iranian-backed rebels a means to squeeze Saudi oil exports, which already had been upended by a drone attack from Iraq that hit the kingdom's crucial East-West oil pipeline.