MOSCOW, May 8 (Reuters) - Moscow has retaliated against sanctions imposed by the United States and Canada last month by expanding its lists of American and Canadian officials barred from Russia, but will not name those affected, the Foreign Ministry said on Thursday. "Sanctions are not our method in general, but unfriendly actions force us to respond. The most recent sanctions (imposed by) Washington and Ottawa are no exception," ministry spokesman Alexander Lukashevich said in a statement. On April 28, the United States slapped visa bans and asset freezes on seven Russian officials close to President Vladimir Putin and imposed sanctions on 17 companies, saying Moscow had failed to abide by an agreement to defuse the crisis in Ukraine. The United States had imposed sanctions on 31 individuals and a Russian bank in March, and Canada has also announced successive rounds of sanctions over Russia's annexation of the Crimea region and its role in the Ukraine crisis. Russia answered the first round of U.S. sanctions with a tit-for-tat response, barring 11 U.S. officials and lawmakers including Senator John McCain and House of Representatives Speaker John Boehner. But Lukashevich said Moscow was not seeking to mirror the U.S. and Canadian sanctions in terms of the number of people affected, and would not reveal the new names on the lists. "Unlike the Americans and Canadians, we have not put on a show," he said, adding that those who are barred from Russia "will find out when they apply for a visa".