"In keeping with our mission of supporting the resilience and integrity of the global financial system as a global and neutral service provider, SWIFT is suspending certain Iranian banks' access to the messaging system," SWIFT said.

The Belgium-based financial messaging service added:

"This step, while regrettable, has been taken in the interest of the stability and integrity of the wider global financial system."

SWIFT's decision has further undermined EU efforts to maintain trade with Iran and save an international deal with Tehran to curtail its nuclear program, after President Donald Trump pulled the US out in May. Being cut off from SWIFT makes it difficult for Iran to get paid for exports and to pay for imports, mostly of oil.