新加坡 H1b 面签approve后additional processing，求助

本人来新加坡出差1-2周，10/21号在新加坡的美国大使馆面签成功，当场approve然后说4-5天会issue。10/22（也就是今天）收到email说要求additional processing，说等待时间不确定要我耐心等待。
Dear Sir,
We refer to your U.S. visa application.While finalizing your application, we identified a need to conduct additional processing on your application.  (Please Note: We do not need any additional information or documentation to complete our processing.)  Your application is in approved status, pending a final security clearance.  We will continue to process your application once the clearances are complete.  The time taken for the clearances varies from case to case and we are unable to expedite the process.  We will  monitor the outcome of your case on a daily basis.  
You may check your application status online athttps://www.ustraveldocs.com/sg/en/step-6/
In the meantime, we appreciate your patience and understanding.

请问论坛上有没有其他的朋友们在新加坡面签遇到过这个情况，这个是什么，和admimistrative processing有区别吗？（问ustraveldoc告诉我不一样但是什么也没说就是耐心等officer）有没有什么方法可以加急或者可不可以给大使馆打电话交流一下加速？本人急需回到美国，这真是当头一棒，希望好心的朋友们可以来交流或者帮忙一下，也希望这个帖子可以给后来的朋友们参考。谢谢。