The letter comes after a CNN report about the impact of the blockade on the ground in Yemen. The investigation revealed that Saudi warships were preventing all oil tankers from docking at the key rebel-controlled port of Hodeidah, including 14 vessels that had gained approval from a United Nations clearance mechanism to berth.Four oil tankers were given rare permission by Yemen’s internationally recognized government — which is backed by Saudi Arabia and its military — to dock between March 31 and April 8. But humanitarian agencies in Yemen have told CNN the fuel is nowhere near enough to deliver aid to millions of people in the country’s north, where pockets of famine have arrived. There have been no indications from the government or Saudi Arabia that it plans to allow the other 10 vessels to berth.The letter, signed by prominent Democrats like House Intelligence Chairman Adam Schiff of California, Judiciary Chairman Jerry Nadler of New York and several members of the Foreign Affairs Committee, specifically calls on Biden to “publicly pressure” the Saudi regime to end the blockade. “This must include guaranteeing that humanitarian and commercial imports can freely enter Yemen; entrusting security oversight to the UN Verification and Inspection Mechanism for Yemen (UNVIM); fully permitting flights in and out of Sana’a airport; and ensuring that crossings for commercial and civilian traffic are permanently opened,” the letter reads.In response to the CNN report, Saudi Arabia’s top diplomat said the country would agree to a UN-backed proposal to end the conflict in Yemen. The proposal would include a ceasefire and the end of the blockade. It was the first time the Saudi government had acknowledged that a blockade of any kind existed. The Houthi and Yemeni governments have yet to agree to the UN proposals.But in an interview with CNN’s Becky Anderson on Monday, Saudi Foreign Minister Prince Faisal bin Farhan Al Saud denied the blockade existed and pointed to the ships that had recently been able to berth at Hodeidah.Saudi Arabia has waged a six-year war in Yemen against Iran-backed Houthi rebels, who drove the internationally-recognized government out of Sana’a in 2015. The conflict has become the world’s worst humanitarian crisis.The State Department has expressed optimism that some fuel ships have been able to dock in Yemeni ports but has made clear that it is only part of the problem. The department remains concerned that the resources coming into the country are not enough for the population’s needs. “The free flow of fuel and other essential goods into and throughout Yemen is critical to support the delivery of humanitarian assistance and other essential activities,” State Department spokesperson Ned Price said on March 24. “The United States appreciates this decision by the Republic of Yemen government. The fuel must go to Yemeni markets without delay to power hospitals, ensure the delivery of food and access to water, and generally help alleviate the suffering of the Yemeni people.”The members of Congress make it clear in their letter that they want the blockade removed in its entirety.They are concerned that the situation in Yemen continues to deteriorate. In their letter, the lawmakers cite estimates that some 16 million people are at risk of starvation due to the blockade. A group of Yemeni Americans from Michigan have been on a hunger strike in solidarity with the Yemenis. Their efforts encouraged their congresswoman, Democratic Rep. Debbie Dingell, to sign on to the letter.”Ending US support for Saudi-led offensive operations in Yemen alone isn’t enough if we allow the blockade to carry on. It’s projected that 400,000 Yemeni children under the age of 5 could die from starvation this year if this blockade continues — it must be lifted now,” Dingell said. “That’s why I was proud today to lead my colleagues in pressing the Biden-Harris administration to use its leverage to end this blockade. With a large Yemeni community in Michigan’s 12th District, I continue to see firsthand the pain and devastation caused to our neighbors as they’ve lost family and friends to this war and the ensuing humanitarian crisis it has caused.” The group on the hunger strike set up in front of the White House on Tuesday and received a visit from Rep. Ilhan Omar, a Democrat from Minnesota. The Biden administration ended support for all Saudi-led offensive operations earlier this year. CNN has reached out to the White House for its response to the letter. A collection of 70 national organizations sent Biden a similar letter with a plea to put pressure on the Saudi government. The signatories to that letter include several prominent celebrities who had endorsed Biden’s presidential campaign, like actors Mark Ruffalo, Amy Schumer and Alyssa Milano.CNN’s Maegan Vazquez and Jennifer Hansler contributed to this report.