UPDATE 1-Ford China starts 2018 in reverse as January sales plunge

* Ford January China sales down 18 pct y/y

* U.S. firm struggling to revive growth in market

* China head departed abruptly last month (Adds details, background)

SHANGHAI, Feb 9 (Reuters) - Ford Motor Co said on Friday its January vehicle sales in China dropped by a sharp 18 percent versus a year ago, marking a difficult start to 2018 for the U.S. carmaker that is struggling to revive its business in the world's biggest auto market.

The bleak number underscores Ford's China woes as it grapples not only with falling sales at a time when rivals are picking up steam, but also with the abrupt departure of its China chief last month who was expected to help drive growth.

Ford sold 75,990 vehicles in the market in January, the firm said in a statement, far slower growth than the wider China auto market which was up 11.6 percent for the month, an industry association said on Friday.

Over the same period, General Motors Co bagged a sales gain of 14.5 percent, while Toyota Motor Corp took home a 24.5 percent rise.

Ford's China head, Jason Luo, stepped down in January after only five months at the helm, a sudden resignation that raised questions over how the automaker will best tackle a sales slump in the world's biggest car market.

The Dearborn, Michigan-based carmaker is hoping to shift gears in China under chief executive Jim Hackett, with a focus on electric commercial cars and vans, which China is encouraging in a bid to clean up its polluted and congested city centres.

"As we reposition our Ford business in China, SUVs (sports utility vehicles), luxury and commercial vehicles are key priorities of our strategy this year," Peter Fleet, head of Ford's Asia Pacific operations, said in a statement.

Foreign automakers are facing fierce competition from Chinese rivals, who are aggressively launching new models to grab market share. A state-backed push towards electric vehicles is also shaking up the market and forcing Ford and others to seek partners and expand local "green" vehicle production.

Ford's China sales slid 6 percent last year, compared with a 3 percent rise for the industry overall. (Reporting by Adam Jourdan; Editing by Himani Sarkar)