万斯：俄方重大让步

Group 1 - The core viewpoint is that the U.S. Vice President reaffirms that the U.S. will not send ground troops to Ukraine but will play a role in ensuring Ukraine's security [1] - The U.S. has observed significant concessions from both Russia and Ukraine in recent weeks, indicating a potential for diplomatic negotiations to end the conflict [2] - The Vice President expressed optimism about the prospects of U.S. diplomatic efforts to resolve the Russia-Ukraine conflict, stating that the U.S. will either succeed gradually or face significant challenges [2] Group 2 - One of the concessions mentioned by the Vice President is Russia's agreement to provide security guarantees to Ukraine [3] - The U.S. has threatened additional sanctions against Russia if there is no progress in peace negotiations within two weeks [3]