* U.S. consumer prices increase, but core CPI moderates
* Fed expected to raise rates on Wednesday (Updates with U.S. market open, adds data, quotes, changes dateline, previous LONDON)
NEW YORK, Dec 13 (Reuters) - The U.S. dollar weakened on Wednesday after consumer price data showed sluggish inflation, adding to concerns the Federal Reserve will be less able to execute multiple rate increases next year.
Excluding the volatile food and energy components, consumer prices ticked up 0.1 percent in November, with the annual increase in the core CPI slowing to 1.7 percent in November from 1.8 percent in October.
The focus is on the core measure of inflation, that came in weaker than the market expected, said Vassili Serebriakov, a foreign exchange strategist at Credit Agricole in New York.
The dollar index against a basket of six major currencies dropped to 93.888, down 0.23 percent on the day.
The weak data comes before a widely expected rate hike on Wednesday, when the U.S. central bank concludes its two-day meeting.
It will probably reinforce the caution of the committee members that are concerned that the Fed is falling short of its inflation target, Serebriakov said. "It also supports our view that the Fed will be fairly gradual next year."
The Fed will announce its decision on rates at 1900 GMT on Wednesday followed by a statement. Chair Janet Yellen will hold a news conference at 1930 GMT.
The Fed on Wednesday may also give its strongest hint yet on how the Trump administration's tax overhaul could affect the U.S. economy.
Investors will pay close attention to how the central bank aims to balance a stimulus-fueled economic boost with the ongoing weak inflation and tepid wage growth that has curbed some policymakers' appetite for higher rates.
President Donald Trump's legislative agenda may be harder to push through, however, following Tuesday's victory by Democrat Doug Jones in the bitter fight for a U.S. Senate seat in deeply conservative Alabama. (Additional reporting by Saikat Chatterjee in London; Editing by Nick Zieminski)