(CNN)President Donald Trump has become increasingly concerned about the humanitarian crisis in Yemen, which has been made worse by years of fighting between Houthi rebels and the Saudi-led international coalition, a United Kingdom official tells CNN.
Trump is 'fired up' about the humanitarian crisis in Yemen
Thousands of civilians have been killed in the fighting, and the country has been hit by a cholera outbreak and famine.
Trump got "fired up" while discussing the crisis during a recent phone call with British Prime Minister Theresa May, the official said.
"He was the most fired up that we've seen him since the chemical weapons attack in Syria," the official said, referring to Trump's expression of anger and disgust over a chemical attack on civilians, including children, by Syrian President Bashar al-Assad's regime earlier this year.
In retaliation, the Trump administration blasted the Syrian airbase that launched the attack with Tomahawk cruise missiles.
During the call with May, Trump sounded angry while discussing the suffering of the civilians and told the prime minister that more pressure must be applied to Saudi Crown Prince Mohammed bin Salman to prevent it, the official said.
The Saudi-led coalition fighting Yemen's Iranian-backed rebels blockaded Yemeni ports in early November after a missile launched from Yemen was intercepted over the Saudi capital of Riyadh.
In a humanitarian gesture earlier this month, Trump called on Saudi Arabia to end its blockade. The Saudi-led coalition said in a statement Wednesday that it would permit the Hudaydah port in Yemen, the last major Houthi-controlled port, to open for 30 days to allow in humanitarian and relief supplies.
The White House issued a statement on Thursday welcoming the decision to re-open the port as well as the willingness to allow US funded cranes to be sent to Hudaydah to aid in the unloading of supplies.
"The United States remains committed to alleviating the dire human suffering in Yemen," the statement said.
Trump and his Secretary of State, Rex Tillerson, "put a lot of muscle" into getting the Saudi-led coalition to re-open the port to humanitarian shipments over the last few weeks, the Deputy Assistant Secretary of State for Arabian Gulf affairs, Tim Lenderking, said later Thursday.
"The benefit of having a strong relationship with Saudi Arabia is that we're very clear and very frank in our private conversations," Lenderking added while speaking to reporters at the State Department.
Trump spoke on the phone Wednesday with Saudi King Salman bin Abdulaziz and "expressed solidarity with Saudi Arabia following the ballistic missile attack against King Salman's official residence" Tuesday, according to a White House statement. The White House said that attack had been "enabled by the Iranian Islamic Revolutionary Guard Corps."
Last week, US Ambassador to the United Nations Nikki Haley held a news conference in which she displayed components of previous Houthi missiles fired into Saudi Arabia and accused Iran of supplying missiles and other weapons to the rebels.
The US and Saudi Arabia have found increasingly common ground on confronting Iran and its proxies; the White House news release on the call between Trump and the Saudi King also said the King had "briefed the President on Saudi Arabia's plan to alleviate the humanitarian crisis in Yemen."
The US military provides aerial refueling support to aircraft from the Saudi-led coalition. The US military also provides what it calls limited intelligence sharing to help Saudi Arabia defend itself from attacks.
The Trump administration has separately ramped up its own counterterrorism activities in Yemen, conducting "multiple ground operations" and launching "more than 120" airstrikes since the beginning of this year, according to a statement issued Wednesday by US Central Command, which oversees US military operations in the region.
Those operations target al Qaeda in the Arabian Peninsula, which is the local al Qaeda affiliate, as well the local branch of ISIS, killing several leaders in October and November, according to Central Command.
Officials say both groups have exploited the chaos of the civil war, with the Central Command statement saying the ISIS branch "has doubled in size over the past year."
"Every strike, every raid and every partnered operation advance the defeat of these violent extremist organizations," Lt. Col. Earl Brown, a military spokesman, said in the statement. "US forces will continue to use all effective measures to degrade the groups' ability to export terror."
Earlier this month the US Agency for International Development announced "nearly $130 million in emergency food assistance" to Yemen, saying the US was "gravely concerned about the worsening humanitarian situation."