Adds background, updates prices

LONDON, Dec 28 (Reuters) - Robusta coffee futures on ICE rose sharply on Thursday with the market supported by supply tightness while raw sugar prices were also higher.

COFFEE

* March robusta coffee LRCc2 rose 2.3% to $2,936 a metric ton by 1444 GMT as the market climbed back up towards a more than 15-year high of $2,970 set a week ago.

* Dealers said supplies remain tight with farmers in top robusta producer Vietnam holding onto newly harvested supplies in the hope that prices will rise further.

* "Farmers are now cultivating fruit trees such as durian and passion fruit alongside coffee trees so they have multiple sources of income and don't have much pressure to release beans," one trader in Vietnam's coffee belt said.

* Premiums in Indonesia also rose due to a scarcity of beans, traders said on Thursday.

* March arabica coffee KCc1 rose 0.2% to $1.9810 per lb.

SUGAR

* March raw sugar SBc1 rose 0.3% to 20.65 cents per lb, edging further away from an 11-month low of 20.03 cents set earlier this week.

* Dealers said the market was finally finding some support after its recent slide which was driven by the strong pace of production in Centre-South Brazil.

* March white sugar LSUc1 rose 0.1% to $595.20 per metric ton.

COCOA

* March London cocoa LCCc1 rose 0.2% to ​3,547 pounds a ton.

* Dealers said there had been some origin price-fixing sales this week as the market consolidates after a sharp rise during the fourth quarter of this year.

* March New York cocoa CCc1 fell 0.5% to $4,259 a ton.

(Reporting by Nigel Hunt; Editing by Kirsten Donovan)

((nigel.hunt@thomsonreuters.com; +44 (0) 7990 561421; Reuters Messaging: nigel.hunt.thomsonreuters.com@reuters.net ))