After days of heavy fighting, Yemeni forces say they have advanced within 20km of the Houthi rebel-held port city of Hodeidah, a vital lifeline where millions of Yemenis get their food and medicine.
Local media reported a major retreat by the rebels on Monday, with the Houthi-appointed governor of the city purported to have fled after coalition forces seized several areas along the Red Sea coast.
"The Yemeni army backed by the coalition is around 20km outside Hodeidah and military operations are ongoing," Saudi coalition spokesman Turki al-Maliki told reporters late on Monday.
Saudi Arabia, together with several other Arab nations, launched a military campaign in Yemen in 2015 aimed at rolling back advances made by the Houthis after they overran much of the country in 2014, including the capital, Sanaa.
Since then, more than 10,000 people have been killed, most of them civilians.
The military coalition has launched more than 16,000 air raids since March 2015, with nearly 1,500 targeting residential areas, more than 200 on school buildings, about 60 against factories and at least 44 targeting mosques.
The fighting in Hodeidah - the country's third-largest city and the main gateway for imports of relief supplies and commercial goods - escalated earlier this year following a flurry of missile attacks against Saudi Arabia.
Riyadh sees Hodeidah port as the entry point of weaponry for the Houthis and has accused its regional rival Iran of sending missiles to the rebels, a charge Tehran has denied.
"Our goal is to cut the vein that the Houthis are benefiting from," Maliki said.
The United Nations has warned any operation aimed at seizing Hodeidah would disrupt the entry of aid shipments to Yemen, 70 percent of which flow through the rebel-held port. The threat of mass famine continues to loom over Yemen.
"The key question isn't whether the coalition can take Hodeidah," tweeted Gerald Feierstein, a former US ambassador to Yemen and a director at the Middle East Institute.
"It's what they intend to do next. Can they use control of the port to ensure humanitarian supplies can get in unimpeded?"
The offensive on Hodeidah is being carried out by a disparate collective of forces including the National Resistance, a group of fighters loyal to Yemen's ex-president Ali Abdullah Saleh, the Tihama Resistance, a group of fighters loyal to Yemen's exiled President Abd-Rabbu Mansour Hadi, and the Giant Brigades, an elite unit backed by the UAE.
The UN says 22.2 million people are in need of aid, with at least eight million on the verge of famine.