Treasury Secretary Janet Yellen urged European allies to act together with the US to find a way to unlock the value of around $280 billion in frozen Russian assets so they can provide sustained financial support to Ukraine.

“It’s vital and urgent that we collectively find a way forward to unlock the value of Russian sovereign assets immobilized in our jurisdictions for the benefit of Ukraine,” Yellen said in excerpts of a speech on the transatlantic alliance she’s set to deliver Tuesday in Frankfurt.

Yellen touted US collaboration with the European Union under the Biden administration in a range of areas, and call for intensified cooperation especially in the field of security, according to the excerpts, released by the US Treasury Monday.

“It’s also critical that we ensure Ukraine has the support it needs to equip its military, fund critical services, and ultimately rebuild in the medium- to long-term,” Yellen said.

The US has been leading a push for the past few months to use these assets to help Ukraine. Options on how to do that have ranged from outright seizing the assets and giving the money to Ukraine, to securitizing them to issue debt, or using them to back some form of loan. 

European countries have reacted with skepticism, raising concerns over the implications such a move would have on financial stability, the role of the euro as well as about the legal risks it could entail. The vast majority of the frozen assets are in Europe.

The topic will be a key focus of discussions between Group of Seven finance ministers meeting in Stresa, Italy later this week. 

The G-7 finance chiefs, who will be joined by their Ukrainian counterpart, are also expected to discuss the effectiveness of their collective sanctions against Russia. 

Yellen also called in her prepared remarks for tightening of the Russia sanctions regime by cracking down on evasion, “including through third parties, and sensitive goods that originate in the US and Europe.”