Washington, DC — An air of uncertainty and mutual resolve swirls over marathon nuclear talks that got underway in Vienna Wednesday (July 2) over whether Iran and six world powers (P5+1) can narrow key gaps to reach a final Iran nuclear accord by July 20.

The United States has sent some 15 officials, led by Deputy Secretary of State Bill Burns and Under Secretary of State Wendy Sherman, to Vienna for talks between Iran and six world powers expected to last over two weeks — an unprecedented investment of top personnel and policy bandwidth that demonstrates the high value Washington has placed on the goal of trying to reach a negotiated agreement with Iran to ensure it does not obtain a nuclear weapon.

Secretary of State John Kerry may also join the talks next week after a July 9-10 trip to China, sources told Al-Monitor, although the decision for Kerry and other foreign ministers to join the talks has not been finalized, amid a fluid situation.

The key gap between the two sides remains over the size of Iran’s enrichment program in a final deal, sources close to the negotiations have told Al-Monitor.