WASHINGTON (Reuters) - U.S. Treasury Secretary Janet Yellen said on Thursday the outright seizure of Russian assets is justifiable but is only one possibility, with assets instead able to serve as collateral for borrowing in the market to help Ukraine.

"That's an option that's been discussed. The leaders have asked us to give them a range of options," Yellen said in an interview with Reuters, when asked if the leading option was pulling forward the interest on those assets to issue bonds or loans for Ukraine.

"The Europeans have taken a very constructive step and that is most of Russian assets held in Belgium ... have now converted to cash and Euroclear earns interest on those assets. The European Union has agreed to segregate that interest and essentially move forward on a program in which it can be transferred to Ukraine. That is an approach that could be broadly supported by countries that are concerned about seizure of assets ... there are a range of options."

(Reporting by Alessandra Galloni; Writing by Lindsay Dunsmuir; Editing by Paul Simao)