WASHINGTON (Reuters) - U.S. Secretary of State Rex Tillerson asked Saudi Arabia to ease its blockade of Yemen, two sources said, just days before the Saudi-led military coalition announced on Wednesday it would let aid flow through the Yemeni port of Hodeidah and allow U.N. flights to the capital.  It was not clear if pressure from Washington was the direct cause of the Saudi change of heart but the request from Tillerson to Saudi Arabia s crown prince, Mohammed bin Salman, was one of several U.S. attempts this month to have Riyadh soften its hawkish foreign policy.  Tillerson asked for a loosening of the blockade on Yemen during a roughly 45-minute phone call at the beginning of this week, according to a source familiar with the matter who spoke on condition of anonymity. R.C. Hammond, a top adviser to Tillerson, confirmed the exchange with Prince Mohammed. The secretary of state  has brought the request to (the) Saudis  attention several times over the past months,  he added.      The Trump administration, according to U.S. officials and a European diplomat, also pressed the Saudis to allow Lebanese Prime Minister Saad al-Hariri to return to Beirut after he flew to Riyadh on Nov.4 and abruptly announced his resignation. The efforts to take the edge off Saudi Arabia s foreign policy reflect growing U.S. concern about Riyadh s direction despite high-profile attempts by President Donald Trump to improve relations with the longtime U.S. ally.              Publicly, Trump, his top aides and senior Saudi officials have hailed what they say is a major improvement in U.S.-Saudi ties compared with relations under former President Barack Obama, who upset the Saudis by sealing a nuclear deal with their arch-foe Iran. Privately, however, U.S. diplomats and intelligence analysts   express growing dismay over Riyadh s foreign policy, especially toward Yemen and Lebanon, as Saudi Arabia aims to contain Iranian influence.      It is my understanding that the administration is frustrated. There has been of course varying degrees of frustration from different members of the administration,  U.S. Senator Todd Young said of the situation in Yemen.  Young, a Republican member of the Senate Foreign Relations Committee, spoke before the Saudi-led military coalition s decision was announced on Wednesday.         The coalition, which is fighting Houthi rebels, said it would allow humanitarian aid access through Hodeidah and U. N. flights to the capital Sanaa, more than two weeks after blockading the country to stop the flow of arms from Iran. Yemen, in civil war and under bombardment by a Saudi-led coalition, faces a deep humanitarian crisis and aid workers warn of famine if the blockade were not lifted.                   A senior Saudi official told Reuters that even before Tillerson and Prince Mohammed spoke recently, senior White House officials had communicated to the Saudi ambassador in Washington the importance of taking those two steps.  They stressed the importance of addressing the humanitarian situation in Yemen and we said that we understood and that the closures were temporary while we work on a comprehensive aid and access plan,  the official said. An administration official, speaking on condition of anonymity, confirmed that White House and National Security Council officials worked on easing the blockade with senior Saudi officials, including Prince Mohammed and his younger brother Khalid, the Saudi ambassador to the United States.    Much of the U.S.-Saudi relationship, multiple U.S. officials say, is conducted in a tight circle and led by Trump s son-in-law and senior adviser, Jared Kushner, who has established a direct channel with Prince Mohammed. Kushner  did not oppose  the pressure on the Saudis and United Arab Emirates to ease humanitarian suffering in Yemen, said one U.S. official. But the official added:  In no way does this change the position that Jared and the Crown Prince evidently share that the main objective is reversing Iranian influence in Yemen and elsewhere.         On Lebanon, the U.S. message to Saudi Arabia about Hariri was conveyed in statements by Tillerson and in private conversations between U.S. and Saudi officials. Those officials included the Saudi state minister for Gulf affairs, Thamer al-Sabhan, who was in Washington recently, a senior administration official said.  We ve encouraged...the Saudis that it will be good for Lebanon s political stability for Hariri to return back to Beirut as soon as is practical,  the official said last week.     Hariri has since returned to Lebanon and shelved his decision to resign as prime minister, easing a crisis that had deepened tensions in the Middle East. Top Lebanese officials have said Saudi Arabia forced Hariri to quit and held him in the kingdom. Riyadh and Hariri deny this. 