European stocks gained ground Monday, with commodity shares among the best performing, giving the benchmark its strongest advance in more than two weeks. "The main thrust of [Monday's] momentum likely arises from the low chances of a U.S. rate rise on Wednesday evening," said Spreadex financial analyst Connor Campbell in a note.

U.S. stocks on Monday closed essentially flat, after trading firmly higher, in a volatile session ahead of the start of a pair of closely watched central-bank policy meetings. Earlier in the session, gains in crude-oil futures and a report showing a surge in home-builder confidence appeared to help lift the equity benchmarks, but those advances evaporated late in the day.

Asian share-trading stayed tentative Tuesday as investors awaited policy decisions from the U.S. Federal Reserve and the Bank of Japan. Markets reflected the uncertain balance between risks and rewards heading into this week's central bank meetings, said Ric Spooner, chief market analyst at CMC Markets.