Explainer-Why is a proposed US-Saudi nuclear pact causing alarm in Washington and the Middle East?

DUBAI, July 22 (Reuters) - The Trump administration backs a nuclear energy pact with Riyadh allowing Saudi Arabiato enrich uranium and process spent atomic fuel, two sources have said, a move that may worry regional states concerned about weapons proliferation. Here are some of the main issues at play: WHAT HAS HAPPENED SO FAR? Washington and Riyadh have for years been discussing a nuclear cooperation deal that would give Saudi Arabia access to U.S. technology and American companies a chance to win big contracts for Saudi atomic energy facilities.