Iran will never hold one-on-one talks with the United States, but could engage in multilateral discussions if Washington returns to the 2015 nuclear deal, Supreme Leader Ayatollah Ali Khamenei said on Tuesday, according to state TV.U.S. President Donald Trump has said he could meet Iranian President Hassan Rouhani, possibly at the U.N. General Assembly in New York later in September."Iranian officials, at any level, will never talk to American officials ... this is part of their (U.S.) policy to put pressure on Iran ... their policy of maximum pressure will fail," state TV quoted Khamenei as saying:"If America changes its behavior and returns to (Iran's 2015) nuclear deal, then it can join multilateral talks between Iran and other parties to the deal," Khamenei added, according to the report.Trump has stepped up sanctions against Iran since last year when he withdrew from the nuclear pact between Iran and six world powers."If we yield to their pressure and hold talks with Americans ... This will show that their maximum pressure on Iran has succeeded. They should know that this policy has no value for us," said Khamenei, who has the last say on all state matters.Tensions between Tehran and Washington have spiked following a weekend attack on major oil sites in Saudi Arabia that the United States said Iran was responsible for. Iran denies the charge.