By Jonathan Landay and Andrea Shalal WASHINGTON, Aug 5 (Reuters) - The U.S. is pressing ahead with talks on allowing Ukraine to make Patriot interceptor missiles, which Kyiv urgently wants to defend against Russian attacks,

Success is not certain, and it will not come as quickly as Mr. Trump would like. But the opportunity is real, and it may not last. If Washington is to test whether this war can be brought to an end, it should act now, before escalation closes the diplomatic opening that exhaustion has begun to create.