U.S. President Donald Trump said Tuesday he prefers to not meet with Iranian President Hassan Rouhani, hours after Iran's supreme leader ruled out a meeting altogether, Anadolu Agency reports.

"I never rule anything out, but I prefer not meeting him," Trump said when asked by reporters on Air Force One if a meeting was still on the table.

Speculation mounted in recent weeks that Trump could meet Rouhani on the sidelines of next week's UN General Assembly gathering in New York. But that appeared to come to a halt when Supreme Leader Ayatollah Ali Khamenei said there would be no talks with the U.S. at any level amid bristling relations that have reached a tipping point after attacks on Saudi oil facilities that crippled the Kingdom's output.

Yemen's Iran-backed Houthi rebels claimed responsibility for the attacks on the Saudi state-run Aramco facilities Saturday.

Trump's has hinted U.S. assessment of the attack point to Iran, but stopped short of directly naming the country as U.S. intelligence develops.

Trump further told reporters aboard the presidential aircraft he is considering five candidates to replace former National Security Advisor John Bolton, whom he dismissed last week, including special presidential envoy for hostage negotiations Robert O’Brien, Army Gen. Ric Waddell, energy department official Lisa E. Gordon-Hagerty, Bolton deputy Fred Fleitz and Army Gen. Keith Kellogg.

He spoke positively of O'Brien, whom he said is "fantastic," and Kellogg who he said he likes "a lot."