The US special envoy for Iran, Brian Hook, is meeting with French, German and British top diplomats in Paris for talks on the Persian Gulf crisis at a time when European powers are trying to save the 2015 nuclear deal struck with Tehran.
European countries want to avoid a further escalation in tensions between the U.S. and Iran and are trying to convince Iran not to leave the nuclear deal, which the U.S. pulled out of last year.
Iran has said it will break out of the nuclear deal's limit on its stockpiles of low-enriched uranium by Thursday, following the re-imposition of U.S. sanctions.
On Wednesday, Iran's U.N. ambassador urged Britain, France and Germany to take "timely" practical steps to preserve the agreement, "which is now in critical condition.