BONN, Germany (Reuters] – It is likely that the United States won’t extend a license to Russia, which allows it to pay U.S. bondholders soon, Treasury Secretary Janet Yellen announced Wednesday. That could make Moscow more vulnerable to defaulting.

Russia has been able to meet its international bond payments despite Western sanctions banning transactions with Russia’s central bank, finance minister or national wealth funds.

There are $40 billion in international bonds held by the country. The last month saw what looked like a sudden U-turn, with payments made to avoid default.

Moscow is now facing a May 25 deadline, when its U.S.-issued licence that allowed it to make U.S. bondsholder payments will expire.

Yellen answered reporters’ questions ahead of a G7 meeting of finance ministers in Bonn if it was possible for the United States to allow the license to expire.

Yellen commented: “If Russia can’t find a solution to their financial problems, they technically default on the debt. I don’t think this is a sign of a substantial change in Russia’s current situation.” Their access to global capital markets is already restricted.

Since the 1917 Revolution, Russia has never defaulted on its foreign debt and it was still rated as investment-grade up to its invasion of Ukraine in February 24th.