Permanent economic sanctions come with a risk, especially when the sanctioned nation doesn't bend to your will. This risk goes double when the U.S. is imposing sanctions to multiple nations.
Those nations could start working together.

Russia and Iran will transfer payments using an alternative system to the internationally recognized SWIFT money transfer network, the governor of the Iranian central bank, Abdolnaser Hemmati, announced.

Instead of SWIFT, a system that facilitates cross-border payments between 11,000 financial institutions in more than 200 countries worldwide, the two countries will use their own domestically developed financial messaging systems – Iran’s SEPAM and Russia’s SPFS.

Back in March Russian banks joined the China International Payments System (CIPS), China's alternative to SWIFT.
However, Iran's decision yesterday was even bigger.

Tehran is set to officially join the Russia-led free-trade zone, the EAEU, next month.

The EAEU FTA includes Belarus, Kazakhstan, Armenia and Kyrgyzstan and they all use the SPFS.
China isn't part of the EAEU, but they do have an FTA with the alliance.
Last year, China launched a yuan-denominated crude oil futures contract on the Shanghai Stock Exchange - the so-called petroyuan - and a few weeks ago Russia began issuing Yuan-denominated bonds.

Europe is late to this trend. Several small banks have joined INSTEX and France has offered $15 Billion in credit, but with strings that Iran has refused.