MOSCOW (Reuters) - President Boris Yeltsin said on Friday he thought it would be necessary to change "one or two" members of his cabinet, but that Viktor Chernomyrdin should stay as prime minister, Russian news agencies said. He also said he did not plan to run in the next presidential election, due in 2000, and had chosen his successor but had not decided when to announce his choice, they said. "The government headed by Viktor Chernomyrdin must be kept on," Itar-Tass news agency quoted Yeltsin as telling Russian media chiefs in the Kremlin. "The government should be stabilised, perhaps, one or two (ministers) should be changed," it went on. "They worked in difficult circumstances," it quoted him as adding. Other agencies reported similar comments, but none elaborated on what cabinet changes Yeltsin might have in mind. Yeltsin, who turns 67 on Sunday, also said he did not plan to stand in elections in the year 2000, and had chosen a preferred successor. A third term is in any case forbidden by Russia's constitution, but aides had earlier hinted there could be legal ways to circumvent this. "I do not intend to violate the constitution. But I have made up my mind about a successor. I now face one problem -- when to announce it," Itar-Tass news agency quoted Yeltsin as saying, adding that he had not discussed his choice with anyone.