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.

The United States and Iran are set to begin a third round of nuclear talks this weekend, entering what experts describe as a more difficult phase of technical negotiations as Washington lays out stricter conditions.