The United States could sanction more banks with ties to Russia and step up enforcement to prevent dodging existing rules, as the West is looking for additional measures to isolate Moscow further ahead of the anniversary of Russia’s invasion of Ukraine on Feb. 24. The West blocked several Russian banks’ access to the international SWIFT payments system soon after Moscow invaded Ukraine in February last year, including two major Russian lenders Sberbank and VTB, which have been forced to scrap operations across much of Europe. Western governments also froze around $300 billion of the Russian central bank’s reserves.

“We have immobilised about 80% of the assets in the Russian banking sector,” head of the U.S. State Department’s Office of Sanctions Coordination O’Brien said.

“We are looking at additional banks and financial institutions to see how Russia deals with the outside world. It is very possible that there will be more action.”

Despite previous sanctions on Russian banks, not all ties have been cut. Some European banks, including UniCredit and Raiffeisen have large businesses in Russia and must follow local rules to grant payment holidays to soldiers.

And Gazprombank, the financial arm of Russian gas exporter Gazprom, has escaped harsh sanctions partly because it handles payments for energy.

Still, some resistance is expected from the European Union, including from Hungary and to a lesser extent from Germany, as they may look to temper further curbs to ease the economic impact. This puts into question how ambitious new restrictions will be.

The United States and European Union have sought to present a united front on sanctions, although their penalties differ, in part because Europe has closer economic ties to Russia.

The European Commission, meanwhile, has proposed that the EU members should cut four more Russian banks, including the private Alfa-Bank, the online bank Tinkoff and the commercial lender Rosbank, from the SWIFT.

Ukraine has called for more sanctions, including targeting Russia’s nuclear sector, but it does not seem to be included. Hungary has already said it would veto such a move.

Moreover, attempts to target Gazprombank would also be met with resistance because of its importance in processing payments for Russian gas, still used by Hungary and other EU states.

O’Brien said that the United States would step up enforcement, something the EU also hopes to improve.

“We are now looking at how sanctions, including financial sanctions, can be most effective,” he said.

“We will see additional measures to increase the intensity of enforcement actions,” he said, adding that although the sanctions allowed global trade in Russian oil and other products, the United States would check on banks and their clients.

“We are always looking to see which companies and parties could benefit from financial transactions linked to Russia,” he said.

The United States has the clout to make sanctions effective because the U.S. dollar is central to global trade, while the EU depends on a patchwork of national authorities, some with scant resources.

The U.S. Treasury has over the last year sanctioned more than 100 individuals and entities seeking to circumvent Russia curbs and has charged prominent Russian oligarchs for violations.

Germany, by contrast, has struggled to enforce sanctions on oligarchs due to legal restraints and reliance on multiple authorities.

“Russia is actively seeking ways to circumvent western sanctions,” said EU trade commissioner Dombrovskis recently, adding that new EU measures would seek to “limit the circumvention of the sanctions”.

“There is a willingness to go further across the European Union,” Irish finance minister McGrath said this week. “We are all appalled about what we are witnessing in terms of continued Russian aggression in Ukraine.”