WASHINGTON (AFP) - The Yemen government is accepting many demands put forward by a rebel Shi'ite militia in a deal to end a deadly political crisis, top US diplomat John Kerry said Wednesday.

Kerry told reporters it was his understanding that the government of President Abdrabuh Mansur Hadi is "going to accept if not all, most of, the objections that the Huthis had," as news of the deal emerged in Sanaa.

He also revealed he would head later Wednesday to the White House for talks on the crisis which has rocked the US ally, a key component of Washington's fight against Al-Qaeda.

"The Huthis had... violent objections to the refusal of the Hadi government to accept all of their demands with respect to the peace and partnership agreement and its implementation," Kerry said after talks with EU foreign policy chief Federica Mogherini.

That had led to violence and "some of the institutions had broken down, and they're in trouble," Kerry said.

He stressed the powerful rebel militia had declared that Hadi was still president, and US officials were waiting to hold another meeting with the beleaguered Yemeni leader.

That would "make a determination from his point of view exactly where things stand," Kerry said, after being asked about the confusing, fluid events in the Yemeni capital, where the militia has fought pitched battles with government forces this week.

"Things are quiet in Yemen as of a little while ago. Our personnel are well-protected, we have strong and multiple personnel there," he said.

Earlier, US officials said Washington was closely monitoring the crisis as officials revealed a US diplomatic vehicle was attacked late Tuesday.

The US military is ready to evacuate American diplomats and other personnel from Yemen, defence officials told AFP, but the State Department has so far not ordered the embassy to close.

State Department spokeswoman Jen Psaki revealed a US diplomatic vehicle had come under attack at a checkpoint near the embassy.

"Huthi gunmen at the checkpoint opened fire on the vehicle, but no injuries were sustained," she told reporters, adding an investigation had been opened.

But she stressed "there has not been a change at this point in our security posture on the ground."

The US embassy in Sanaa has been operating on "a bare minimum" of staff since September, when the militia seized almost all of the capital, Kerry stressed.