BRASILIA, Jan 4 (Reuters) - Brazil posted a trade deficit of $42 million in December, official data showed on Monday, compared with the consensus forecast in a Reuters poll of economists of a $200 million surplus, bringing the 2020 annual surplus to $51 billion. Exports in December totaled $18.365 billion and imports were $18.407 billion. The total 2020 surplus was up 6% from the previous year’s $48.1 billion surplus, the Economy Ministry said, adding it expects a $53 billion surplus this year. (Reporting by Jamie McGeever Editing by Chris Reese)