A Saudi-led coalition has made no major gains in its offensive to wrest control of Yemen's Hodeida port from the Iran-aligned Houthis, leaving it without the decisive increase in leverage it had sought against the group in U.N.-sponsored peace efforts.

The alliance led by Saudi Arabia and the United Arab Emirates launched the offensive on the heavily defended Red Sea city on June 12 in the largest battle of the three-year war, which the United Nations fears risks triggering a famine.

The Arab states pledged a swift operation to take over Hodeida's air and sea ports, without entering the city center. But they have made little progress in the campaign which Riyadh and Abu Dhabi say aims to cut off the Houthis' main supply line and force the group to the negotiating table.

The coalition announced on June 20 that it had seized Hodeida airport, but local military and aid sources told Reuters that neither side has complete control of the airport and its surrounding area, which spreads over 20 km (12 miles). "The coalition never took control of the airport," Houthi leader Mohammed Ali al-Houthi told Reuters.

The Houthis, who control the most populated areas of Yemen including the capital Sanaa, are adept at guerrilla warfare. Houthi fighters have been harassing UAE-led forces near the airport and on the coastal road that the coalition uses to resupply its forces from military bases on the western coast.