The US is pressuring Iran to cease supplying military drones to Russia as part of negotiations on a larger unwritten agreement between Washington and Tehran to de-escalate tensions, according to the Financial Times, citing sources briefed on the topic.

The US is pressuring Iran to cease sending armed drones to Russia, which Moscow is utilizing in the Ukraine conflict, as well as replacement parts for the unmanned aircraft, according to the report, which cited an Iranian official and another person involved with the negotiations.

The White House and Iran’s foreign ministry did not immediately respond to a Reuters request for comment.

The news comes as Washington and Iran are trying to ease tensions and revive broader talks over Iran’s nuclear program. US Secretary of State Antony Blinken said on Tuesday that he would welcome any Iranian steps to de-escalate its “growing nuclear threat.”

These discussions have taken place alongside the negotiations on a prisoner exchange deal last week, the newspaper said. Iran allowed four detained U.S. citizens to move into house arrest from Tehran’s Evin prison while a fifth was already under home confinement.

Last week, sources told Reuters that Iran may free five detained U.S. citizens as part of a deal to unfreeze $6 billion in Iranian funds in South Korea.