A view of the Goldman Sachs stall on the floor of the New York Stock Exchange July 16, 2013. REUTERS/Brendan McDermid/File Photo

(Reuters) - Citigroup downgraded Goldman Sachs Group Inc GS.N to "sell" citing valuation, sending its stock down as much as 1.6 percent and making it the biggest drag on the Dow Jones Industrial Average .DJI.

Citi analyst Keith Horowitz said Goldman would need an additional $4 billion of revenue above current full-year estimates to bridge the gap between current and expected return on tangible equity.

“While we expect Goldman will see improved trading revenues going forward, the path is relatively uncertain and the bar is relatively high,” Horowitz wrote in a note to clients.

Analysts on average are expecting 2017 revenue of $32.32 billion, according to Reuters data.

The downgrade comes days before the large U.S. banks start reporting fourth-quarter results, their first after the election in November and the Federal Reserve’s rate hike in December.

Goldman is expected to report on Jan. 18.

Bank stocks have been on a tear since the U.S. election, with the KBW Bank Index .BKX rising 22.6 percent. Goldman Sachs' shares rose 33.5 percent during the period.

The stock was down 0.9 percent at $240.58 in morning trading.