Secretary of State John Kerry Monday praised Qatar for its help in trying to resolve the crisis in Yemen, amid hints the US is in contact with Shiite rebels through go-betweens.
The Huthi militia Sunday set a three-day deadline for political parties to resolve the power vacuum in Yemen left after the president and prime minister offered to resign last month.
The Huthis' lightning offensive when they seized the presidential palace and key government buildings on January 20, plunged the country deeper into crisis and prompted US-backed President Abedrabbo Mansour Hadi and his premier to tender their resignations.
It has complicated the US fight against Al-Qaeda in the Arabian Peninsula (AQAP) branded by the US one of Al-Qaeda's most dangerous branches.
Meeting with Qatari Foreign Minister Khalid al-Attiyah at the State Department on Monday, Kerry said he was grateful for the "many ways in which Qatar, the emir, and Dr Attiyah have made themselves available in order to be of assistance."
"Most recently, they were particularly helpful with respect to Yemen and our efforts in the last few days to deal with some of the adjustments necessary to what has been happening there."
Asked later at a forum at the Atlantic magazine what Kerry meant, Attiyah did not go into details.
"We've been closely talking to our friends about the GCC initiative and how we can enhance the solution," the minister said.
In 2011, the monarchies of the Gulf Cooperation Council (GCC) urged the then president to sign a power transfer plan ending the country's political turmoil.
But the new crisis has raised fears that impoverished Yemen, which lies next to oil-rich Saudi Arabia, could become a failed state.
Last week, the Pentagon said US officials were holding discussions with representatives of the Shiite militia but were not sharing intelligence on Al-Qaeda in Yemen.
"Given the political uncertainty, it's fair to say that US government officials are in communication with various parties in Yemen about what is a very fluid and complex political situation," said Pentagon spokesman Rear Admiral John Kirby.
The Wall Street Journal last week reported that US officials were in touch with Huthi fighters largely through intermediaries.
"We have to take pains not to end up inflaming the situation by inadvertently firing on Huthi fighters," a senior US official told the Journal.
"They're not our military objective. It's AQAP and we have to stay focused on that."