The Kremlin on Thursday underscored Russia’s opposition to NATO membership for Ukraine, warning that such a move could derail efforts to end the conflict in eastern Ukraine, as leaders of the alliance gathered for a key summit in Wales. Russian Foreign Minister Sergei Lavrov also told the United States not to try to impose its own will on Kiev. Lavrov’s comments came one day after Russian President Vladimir Putin announced a plan to end the fighting that would entrench gains by pro-Russian rebels and hand a significant defeat to Ukrainian leaders who have sought to regain full control of their nation. Lavrov said Ukraine’s attempts to abandon its nonaligned status by joining the NATO alliance could “derail all efforts aimed at initiating a dialogue with the aim of ensuring national security,” according to the Russian news agency ITAR-TASS. He said Russia was ready to take “practical steps” to de-escalate the crisis under the proposals made by Putin. “We hope that the calls [by Putin] will be heard, especially by Kiev, [and the rebel leaders of] Donetsk and Luhansk,” he was quoted as saying by the Interfax news agency.