Iran and the United States prepared Saturday to start in-depth negotiations in Oman over Tehran's rapidly advancing nuclear program, talks that likely will hinge on the Islamic Republic's enrichment of uranium.

Top Iranian and U.S. negotiators will meet again on Saturday to hammer out a new deal curbing Tehran's advancing nuclear programme, while U.S. President Donald Trump signalled confidence in clinching a new pact that would block Iran's path to a nuclear bomb.

Plans for a third round of talks in three weeks have raised hopes for an Iran nuclear accord, which could avert a new Mideast conflict. President Trump said he believed a deal was within reach.