On a visit to Washington, German Foreign Minister Heiko Maas appealed to both powers to save the Intermediate-Range Nuclear Forces treaty (INF) but pointed the finger at Russia.
"The ball is still in Russia's court," he told reporters after talks with Secretary of State Mike Pompeo.
While welcoming that Washington and Moscow had held talks, Maas criticized the existing Russian proposals as insufficient.
Russia "so far has not been willing to establish complete transparency," Maas said. "Just looking at one missile won't be enough."
The United States has declared Russia to be in violation of the treaty - which bans ground-launched missiles with a range of between 500 and 5,500 kilometers.
It last month gave a 60-day deadline, which ends on February 2nd, for Moscow to stop the alleged breach, saying that the United States otherwise will begin a six-month process of formally withdrawing from the treaty.
Russia denies that it is violating the treaty. At a briefing Wednesday in Moscow, Russia for the first time revealed the missile in question -- the 9M729 -- but insisted that its maximum range was 480 kilometers.
The EU has appealed for the preservation of the INF, one of the enduring security treaties in Europe, which was signed in the waning days of the Cold War by US president Ronald Reagan and Soviet leader Mikhail Gorbachev.
Until the February 2nd deadline, "all opportunities must be taken advantage of to pressure the Russian side into complying with the treaty again," Maas said.