America is still talking to Russia about a deal to free jailed weed-smuggler WNBA player Brittney Griner and ex-US marine Paul Whelan but Moscow has not provided a “serious response” to any of its proposals, a senior U.S. diplomat said in comments published on Monday.

Elizabeth Rood, the U.S. chargée d’affaires in Moscow, told Russia’s state-owned RIA news agency that talks were continuing through the “designated channel.”

“The United States, as we have said, has put a significant proposal on the table. We have followed up on that proposal and we have proposed alternatives,” she said. “Unfortunately, so far the Russian Federation has not provided a serious response to those proposals.”