美国制裁俄罗斯石油公司，有效吗？为什么现在实施

Group 1 - The U.S. has imposed significant sanctions on Russian oil giants Rosneft and Lukoil, targeting their assets in response to Russia's ongoing military actions in Ukraine [1][3][5] - The sanctions include freezing all U.S. assets of these companies and extending to their subsidiaries, with potential secondary sanctions on foreign banks that engage with them [3][5] - The sanctions are expected to impact Russia's energy exports significantly, as Rosneft and Lukoil account for nearly half of Russia's oil exports [5][15] Group 2 - The sanctions are part of a broader strategy involving U.S. allies, including the UK and EU, who are also preparing to announce new sanctions against these companies [5][11] - Domestic pressure in the U.S. is mounting for strong actions against Russia, with public support for sanctions and Republican lawmakers criticizing any perceived softness towards Russia [11][19] - The effectiveness of these sanctions in compelling Russia to negotiate remains uncertain, as Russia has adapted to previous sanctions and established alternative trading partnerships [19]