LONDON, Sept 13 (Reuters) - The United States" chaotic withdrawal from Afghanistan has raised questions for its Arab allies in the Middle East about whether or not they can continue to rely on Washington, a senior Gulf Arab official said on Monday. U.S. allies fear the Taliban"s return and the vacuum left by the West"s chaotic withdrawal will allow militants from al Qaeda to gain a foothold in Afghanistan 20 years after the Sept. 11, 2001 attacks on the United States. "Afghanistan is an earthquake, a shattering, shattering earthquake and this is going to stay with us for a very, very long time," the Gulf Arab official said on condition of anonymity due to the sensitivity of the diplomacy. "Can we really depend on an American security umbrella for the next 20 years? I think this is very problematic right now – really very problematic." Gulf Arab allies of the United States find the way that U.S. foreign policy appears to oscillate with "180-degree shifts" problematic and fears that militants will gain a foothold in Afghanistan, the official said. The official said that the withdrawal of the United States had sent a message to militants across the world that all they had to do was to continue their fight. "We don’t know how this Afghan regime will turn out – we think most probably it will be the same Taliban. Slightly more world savvy but not by much," the official said. The official said that if there was to be a geopolitical struggle over Afghanistan it would be between China and Pakistan on the one hand and Russia, Iran and India on the other. The United States, the official said, would not be part of that struggle. "If there is a geopolitical struggle over Afghanistan, we will see Pakistan and China on one hand and we will see India, Iran and Russia on the other hand," the official said. "And I don’t think the Americans are going to be a part of the geopolitical struggle over Afghanistan."