Washington, Dec 15 : Top US and European nations officials fear that Ukraine will fall to Russia if the aid package continues to falter in the US Congress, predicting the imbroglio could have a "potentially debilitating impact on Ukraine's defence and longer-term prospects of losing the war". "There is no guarantee of success with us, but they are certain to fail without us," a senior US military official was quoted by CNN as saying. At the centre of this stalled military aid flow to Ukraine is the impact on Ukraine's on-going counter-offensive in the east and south, where its forces have struggled to make significant forward progress. "If looking at taking and holding further territory," said one European diplomat, "it is hard to see how that could succeed without continued US support". Ukraine President Volodymyr Zelenskyy had air dashed to Washington and met President Joe Biden, Speaker Mike Johnson and top Senators and Congressmen in a valiant bid to have the aid flow continue to his country fighting with its back to the wall. He even made a powerful address to the Senate to continue the aid flow. Republican hardliners had blocked Biden's omnibus over $100 billion combined military and humanitarian Israel -Ukraine aid package allowing $16 billion to Israel while rejecting the $61 billion aid to Ukraine saying the funds were better deployed on the southern borders where there was a massive influx of illegal migrants from South America rocked by political disturbances such as in Venezuela and Mexico. Western officials are afraid that loss or further delay of US support to Ukraine will also impact aid from its allies. On Friday, Ukraine suffered a major blow when Hungary blocked further European Union aid, though talks on the issue are expected to resume in January. The news underscored that Kiev was facing a major challenge and many fear that if the US fails to continue providing support, European nations will follow, media reports said. Intelligence agencies are currently assessing the timelines of how long Ukraine could hold Russia without US and NATO help. A summer defeat of Ukraine was forecast by one senior US military official. A Russian victory would not just be bad news for Ukraine, it would be a disaster for wider European security and a major blow to the US. /IANS