The Pentagon has acknowledged for the first time that it has deployed troops to Yemen more than a year after pulling out following military intervention by the Arab-led coalition.
The security void created after more than a year of war between loyalists of exiled government of Abd-Rabbu Mansour Hadi and the Shia Houthi rebels has been exploited by the al-Qaeda in the Arabian Peninsula (AQAP).
Pentagon spokesman Jeff Davis said on Friday that the United States military had also stepped up air strikes against AQAP fighters in the war-torn country.
A "very small number" of American military personnel has been working from a "fixed location" with Yemeni and Arab coalition forces - especially the Emiratis - in recent weeks around Mukalla, a port city seized by AQAP a year ago, Davis said.
"This is of great interest to us. It does not serve our interests to have a terrorist organisation in charge of a port city, and so we are assisting in that," the spokesman added.
He said the troops were helping the Emiratis with "intelligence support", but declined to say if they are special operations forces.
AQAP fighters have now fled Mukalla and other coastal areas, due to the government offensive.
The US is also offering an array of assistance to partners in Yemen, including air-to-air refuelling capabilities, surveillance, planning, maritime security and medical help.
String of attacks
The Pentagon previously had more than 100 special operations forces advising the army in Yemen, but pulled them out early last year as the country collapsed.
The US Navy also has several ships nearby, including an amphibious assault ship called the USS Boxer and two destroyers.
AQAP took advantage of the chaos of fighting between pro-government forces and Iran-backed rebels to expand its control in southern Yemen, including the seizure of Mukalla.
The Pentagon announced it has carried out a recent string of strikes on AQAP in recent weeks, outside of Mukalla.
"We have conducted four counterterrorism strikes against AQAP since April 23, killing 10 Al-Qaeda operatives and injuring another," Davis said.
The US periodically targets AQAP in Yemen, including a strike in March on a training camp that killed more than 70 fighters.
The group claimed responsibility for last year's attack in Paris on the staff of satirical weekly Charlie Hebdo, and has been linked to more than one attempt to blow up aircraft bound for the US.
The Yemen conflict has killed more than 6,400 people and displaced 2.8 million since March last year.