AL-MUKALLA, Yemen — The United Arab Emirates has sent a military brigade to aid fighters battling Houthi rebels in Yemen, senior Yemeni and United States military officials said Monday, in a move that threatened to escalate a regional struggle between Iran and the monarchies of the Persian Gulf.

The Emirati troops landed in the southern port city of Aden in recent days, bringing with them tanks and other armored vehicles, the officials said. They quickly had an effect, participating in a rout of Houthi fighters on Monday from one of Yemen’s largest and most strategically important air bases, according to a senior Yemeni military commander.

A coalition of Sunni Arab states, led by Saudi Arabia and including the United Arab Emirates, has been waging a bombing campaign against the Houthis since late March — largely driven by the view that the Houthis, a Shiite-led movement from northern Yemen, is fighting on behalf of Iran, Saudi Arabia’s regional rival.

The Houthis acknowledge their alliance with Iran but deny that they are acting as its proxy. The Obama administration has said that the Saudis are exaggerating the ties between Tehran and the Houthi rebels, who control Sana, the capital, and other parts of Yemen. The criticism has not deterred the Saudis from carrying out thousands of airstrikes and imposing an air and maritime blockade around Yemen as part of an aggressive offensive that aid workers say has helped fuel a humanitarian crisis.