LONDON, Dec 24 (Reuters) - London cocoa futures closed lower on Wednesday weakened partly by the strength of sterling against the dollar while sugar and robusta coffee prices rose.

London-based cocoa, robusta coffee and white sugar contracts had an abbreviated session on Wednesday and will be closed on Thursday and Friday for the Christmas holidays.

New York-based cocoa, arabica coffee and raw sugar markets will be shut on Thursday but reopen on Friday.

COCOA

* London cocoa LCCc1 settled 2% lower at 4,216 pounds a metric ton.

* Dealers said a short covering bounce appeared to have run out of steam with the focus returning to weak demand and the prospect of a global surplus in the 2025/26 season.

* New York cocoa CCc1 fell 0.6% to $5,924 a ton by 1234 GMT.

COFFEE

* Arabica coffee KCc1 fell 0.4% to $3.4560 per lb.

* Dealers said the outlook for next year's crop in top arabica producer Brazil appeared to be improving although a pick-up in roaster buying after the recent decline in prices had helped underpin the market.

* Robusta coffee LRCc2 settled 0.9% higher at $3,858 a ton with farmer selling in top robusta producer Vietnam slowing after the recent fall in prices.

SUGAR

* Raw sugar SBc1 was up 0.7% at 15.31 cents per lb.

* Raw sugar speculators trimmed a net short position by 4,630 contracts to 1,056 in the week to Dec. 16, according to CFTC data.

* White sugar LSUc1 ended 0.8% higher at $435.20 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/))