The United States will speed up weapons deliveries to members of the Saudi-led coalition launching airstrikes against Iran-aligned Shiite rebels in Yemen, a top American diplomat said Tuesday.  

Deputy Secretary of State Antony Blinken blamed the rebels, known as Houthis, for creating political and economic instability in Yemen that Al Qaeda seeks to exploit. 

"We have expedited weapons deliveries, we have increased our intelligence sharing, and we have established a joint coordination and planning cell in the Saudi operations center," he said in a statement to reporters after meeting with Saudi royals and Yemen's President Abed Rabbo Mansour Hadi, who fled his country due to Houthi advances and is currently in Saudi Arabia.

Intelligence sharing includes making available raw aerial imagery the coalition could use to better strike anti-Hadi forces, a U.S. defense official not authorized to comment publicly told the Associated Press. Blinken said the U.S. and the six-nation Gulf Cooperation Council must coordinate closely and press all parties to seek a political solution.

A Pentagon spokesman told Fox News that the joint coordination cell was established at the beginning of the conflict late last month. Pentagon press officer Col. Steve Warren said recently that a "handful" of U.S. advisers were working there, but did not specify an exact number. 

A U.S. military officer with knowledge of the planning cell also told Fox News that the U.S. was doing more to help the guide the Saudi planes. The officer said most of the guidance was designed to make sure the jets hit their targets and did not strike large population centers. 

The Saudi-led coalition began carrying out airstrikes to support forces loyal to Hadi on March 25. The Saudi-led air campaign supporting Hadi, which began on March 25th, has so far failed to stop the Houthis' advance on Aden, Yemen's second-largest city, which was declared the provisional capital by Hadi before he fled the country for Saudi Arabia as the rebels closed in two weeks ago.

The World Health Organization warned Tuesday of an unfolding humanitarian crisis, saying at least 560 people, including dozens of children, have been killed, mostly in the air campaign and ground battles. The aid group said that over 1,700 people have been wounded and another 100,000 have fled their homes as fighting has intensified over the past three weeks.

Tons of desperately needed medical supplies await clearance to be flown into Yemen, including a Red Cross shipment that would be the first aid to reach Yemen since the start of a Saudi-imposed air blockade.

Late Tuesday, the group said a cargo plane with 17 tons of medical supplies was in Jordan awaiting the go-ahead from coalition forces to land in the Yemeni capital, Sanaa, hopefully on Wednesday. Another 35 tons of supplies were also ready for shipment.

On Wednesday, Human Rights Watch said witnesses told it that Houthi forces fired into crowds of demonstrators in the cities of Taiz and Torba the day before the bombing campaign began, killing at least 7 people and wounding over 83 others. The New York-based group called on Houthi authorities to investigate the incidents.

"Yemen's spiraling conflict is causing a calamitous breakdown in law and order," said Joe Stork, deputy Middle East and North Africa director at Human Rights Watch. "Security forces in control, whatever side they are on, have responsibilities to uphold and protect people's rights and to take action against their members who commit abuses."

Fox News' Lucas Tomlinson and the Associated Press contributed to this report.