NEW YORK (AFP) - Wall Street stocks finished slightly higher on Tuesday (Sept 20) ahead of a closely-watched policy announcement by the Federal Reserve.

The Fed is not expected to raise rates Wednesday, as US economic data continues to show some signs of weakness and inflation remains weak. Many analysts expect an interest rate hike later this year, perhaps in December.

Analysts are also awaiting a policy announcement by the Bank of Japan that some believe could entail additional stimulus.

The Dow Jones Industrial Average climbed 0.1 per cent to 18,129.96.

The broad-based S&P 500 gained less than 0.1 per cent to 2,139.76, while the tech-rich Nasdaq Composite Index advanced 0.1 per cent to 5,241.35.

Wells Fargo rose 1.2 per cent despite enduring tough questioning at a Senate hearing on its bogus accounts scandal. Shares of the bank fell nearly seven percent last week in the aftermath of news the bank paid US$185 million (S$250 million) in penalties for opening some two million accounts without customers' knowledge.

Dow member ExxonMobil dropped 1.5 per cent after the Wall Street reported that US securities regulators were investigating whether it boosted its financial statements with unrealistic accounting for low oil prices and the potential impact of climate mitigation policies.

Tobira Therapeutics, which specializes in remedies for liver disease, surged more than eight-fold on news it agreed to be acquired by Allergan for US$1.7 billion. Allergan lost 2.7 per cent.

Other biotech shares were boosted, with Amgen and Biogen winning more than 1 per cent each and Gilead Sciences 3.5 per cent.

Shares of Marriott International and Starwood Hotels & Resorts Worldwide rose 2.3 per cent and 2.4 per cent, respectively, after announcing that their merger had won Chinese approval, the last regulatory hurdle to completing the deal.