COPENHAGEN (Reuters) - Leaders of three of the eight parties elected in Iceland in an October 28 parliamentary election began formal coalition negotiations on Tuesday, state broadcaster RUV reported. The Independence Party, the Left-Green Movement and the center-right Progressive Party, are seeking to form a government after talks between four leftist parties broke down last week. It should be clear by the end of the week whether talks have made progress. President Gudni Johannesson has not yet given any party leaders a formal mandate to try to form a government. 