European stocks swung between small gains and losses on Tuesday, with investors staying cautious ahead of this week's Federal Reserve meeting that will be scrutinized for hints on future U.S. monetary policy. The Stoxx Europe 600 index SXXP, +0.04% ended marginally higher at 382.12, after trading in a relatively tight range during the session.

U.S. stocks extended gains Tuesday with all three main benchmarks closing at records as the Federal Reserve began its two-day policy meeting where they are expected to finalize the details on the unwinding of its $4.5 trillion balance sheet. The Dow Jones Industrial Average DJIA, +0.18% rose 42 points, or 0.2%, to end at 22,373, its sixth straight record finish, while the S&P 500 SPX, +0.11% added 2 points, or 0.1%, to 2,506, logging its fourth record close in a row.

Equity trading across Asia was muted early Wednesday on caution before the U.S. Federal Reserve's policy announcement. After a solid start to the week, markets were treading water as investors awaited monetary policy guidance from the Federal Open Market Committee. Most investors aren't expecting interest rates to rise.