The Society for Worldwide Interbank Financial Telecommunication began blocking Iranian banks from using its communications network on Saturday, NPR reported.
"It's a big deal," Iran sanctions expert Mark Dubowitz told NPR. "Because it complicates Iran's ability to move billions of dollars through the international financial system."
Iran's international trade depends on these financial transactions. SWIFT's move not only impedes the nation's oil exports, but imports of crucial infrastructure commodities, like steel, as well.
The sanctions are part of a continued effort by the U.S. and EU nations to pressure Iran into opening up its nuclear energy program to international inspection to uncover any efforts to develop nuclear weapons.
An inspection team from the U.N.'s International Atomic Energy Agency arrived in Iran last month, and upon completing its report, expressed some concerns about its nuclear ambitions.
"The agency continues to have serious concerns regarding possible military dimensions to Iran's nuclear program," said IAEA Director Yukiya Amano in a March 5 statement.
Israel has made it clear that it will carry out military strikes on Iran's energy infrastructure if it feels Iran has the capacity to develop nuclear weapons.
President Barack Obama recently reiterated U.S. support for Israel and its right to defend itself during a state visit by Israeli Prime Minister Benjamin Netanyahu, although he cautioned the Israelis against aggressively pursuing military action.
"Already, there is too much loose talk of war," Obama said during a March 4 conference of the pro-Israel lobby, AIPAC. "Over the last few weeks, such talk has only benefited the Iranian government, by driving up the price of oil, which they depend on to fund their nuclear program. For the sake of Israel's security, America's security, and the peace and security of the world, now is not the time for bluster."