Russian Foreign Minister Sergey Lavrov said that US pressure on the SWIFT payment system was unacceptable, TASS reported.

"Now, within a joint group of participants of the Joint Comprehensive Plan of Action (JCPOA) [on the Iranian nuclear program], mechanisms are being worked out that will make it possible to continue implementing the provisions of this document, primarily with regard to economic ties with Iran and without US participation," Lavrov said.

"This is not an easy task. You see, what unacceptable methods have already been used to put pressure on SWIFT system operators," the minister stressed.

"But experts are working intensively on this issue. They have a fairly stable understanding that this is possible and that such measures will be found," he added.

The minister said that the US sanctions against Iran are absolutely illegitimate.

"As for the US measures against Iran, they are absolutely illegitimate. They are taken as a flagrant violation of the UN Security Council's decision," Lavrov said.

"We proceed from the fact that no one has abolished the norms of not only international law, but also of international communication, and it is hardly permissible to pursue a policy based on ultimatums and unilateral demands in our time," he added.

"We proceed from the fact that the JCPOA, which was signed and approved unanimously in 2015 by the UN Security Council, retains its strength for those who retained their participation in this mechanism. After the US’s exit from the JCPOA, both Europeans and Russia confirmed their participation in it as well as China, and Iran itself," the Russian Foreign Minister added.

SWIFT (the Society for Worldwide Interbank Financial Telecommunication) provides a network that enables banks worldwide to send and receive information about financial transactions.