WASHINGTON — U.S. consumer prices were unchanged in November as declines in energy and food held down overall costs. But core inflation was up 2 percent over the 12 months ending in November. That was the fastest pace in more than a year and the kind of increase Fed officials want to see to justify the start of a round of interest rate increases.

The flat reading for consumer prices last month followed a modest 0.2 percent increase in October and outright declines in August and September, the Labor Department reported Tuesday. Core inflation, which excludes energy and food, was up 0.2 percent in November and has risen 2 percent over the past 12 months, the fastest gain since a similar 2 percent rise for the 12 months ending in May 2014.

Over the past year, overall inflation has risen just 0.5 percent. Overall prices are being held back by a sharp fall in energy costs and a stronger dollar, which makes imports cheaper. Fed Chair Janet Yellen has said she expects both of those impacts will soon start to fade and because of that she expects overall inflation will start rising back to the Fed’s 2 percent target.

Private economists said Fed officials, who were holding their final meeting of the year on Tuesday and Wednesday, are likely to use the rise in core prices as justification to support a quarter-point rate hike at this meeting, the first rate increase in nearly a decade.

Paul Ashworth, chief U.S. economist at Capital Economics, said he expects rising inflation will prompt the Fed to raise its key interest rate to near 2 percent by this time next year. This rate has been at a record low near zero for the past seven years. Other economists are predicting a much more gradual rise in rates of less than half that amount to around 1 percent for the Fed’s benchmark federal funds rate.