Millions of people in northwest Syria face disaster if the United Nations fails to approve an extension of cross-border humanitarian operations next month, a senior U.N. aid official said on Thursday. Some 3 million people, many of them displaced by fighting elsewhere in Syria during the decade-long conflict, have sought shelter near the border with Turkey, outside the control of President Bashar al-Assad"s government. Access for cross-border aid from Turkey was reduced last year to just one crossing point after opposition from Russia and China - permanent Security Council members - to renewing other crossings. A new showdown is likely next month when the operation"s mandate must be renewed. "It"s going to be a disaster if the Security Council resolution is not extended. We know that people are really going to suffer," said Mark Cutts, U.N. deputy regional humanitarian coordinator for the Syria crisis. "Our expectation from the council is that they put the needs of the civilians first," Cutts told Reuters at an aid supply centre in the Turkish border town of Reyhanli. "In northwest Syria you have some of the most vulnerable people anywhere in the world." Currently around 1,000 U.N. trucks a month enter Syria at the single crossing point of Bab al-Hawa to deliver food, medical supplies and humanitarian aid, trying to meet the needs of four out of five people in northwest Syria. "This is their lifeline," U.S. ambassador to the United Nations Linda Thomas-Greenfield told reporters on a visit to the area. "Over the last year and a half some members of the Security Council succeeded in shamefully closing two other crossings into Syria." "Bab al-Hawa is literally all that is left ... If it is closed it will cause senseless cruelty." Announcing an additional $240 million in funding for Syrians and their host communities, Thomas-Greenfield said she was also willing to work with Russia to find ways for aid to be delivered "cross-line" from Syrian government-controlled areas. Russia, which supports Assad, has accused his Western opponents of ignoring the role that could be played by supplies brought cross-line from Damascus. "We have spent more than one year negotiating on both sides to have both cross-line and cross-border aid," Cutts told the U.S. envoy in a briefing near the border. "Despite all our efforts, we have not managed to get a single truck cross-line. This is not for a lack of trying from the UN side, but rather because it is a war zone." In addition to the difficulties over restricted access, the aid operation was starved of cash, he said. "What we really need is to scale up funding. We need more access, not less. Take that back with you to the United Nations Security Council,” Cutts told Thomas-Greenfield.