SOFTS-ICE sugar climbs as economic optimism buoys commods

* Rebalancing of Rogers index to boost robusta coffee

* Speculators trimming huge net short in ICE sugar

* Ivorian cocoa grind to shut for up to three months

(Adds quotes, updates prices)

LONDON, Jan 30 (Reuters) - Raw sugar futures on ICE rose on Wednesday, supported by broad-based gains in commodity markets, some constructive chart signals and the potential for fund short covering.

Arabica coffee on ICE edged up but remained rangebound while cocoa was little changed.

Oil and many other commodities rose on Wednesday on optimism about the global economy ahead of a U.S. Federal Reserve policy decision.

March raw sugar futures on ICE were up 0.31 cents, or 1.7 percent, at 18.69 cents a lb at 1249 GMT. The contract rose to a peak of 18.96 cents on Monday before producer selling stalled the rally.

"It seems we may well have a test of 19 cents and the stops probably just above but it would probably be another sell opportunity for the jobbers," Thomas Kujawa of Sucden Financial said in a note, adding the medium-term outlook was bearish.

Dealers said speculators have started to cover a net short position which has risen to the largest in seven years, according to data issued last week by the U.S. Commodity Futures Trading Commission.

Front month raw sugar prices fell to 18.06 cents a week ago, the lowest level in more than two years, following a prolonged decline driven by surplus global supplies.

March white sugar on Liffe rose $6.50, or 1.3 percent, to $494.30 a tonne.

Robusta coffee futures on Liffe were higher with the market expected to derive support from a rebalancing of the Rogers International Commodity Index.

The index is including robusta coffee for the first time with a 2 percent weighting. The change is to be implemented in the January roll period which begins today and ends Friday.

"For robusta it will definitely be quite an important impact," Romain Lathiere, head of dealing at Diapason Commodities Management said.

March robusta coffee rose $13 or 0.7 percent to $1,949 a tonne.

The rebalancing is bearish for ICE arabica coffee which will no longer be a component of the index.

INDEX REBALANCED

Other changes in the Rogers index include a switch to Liffe cocoa from ICE cocoa, the addition of Liffe white sugar and a reduction in the weighting for ICE raw sugar.

Arabica coffee prices remained rangebound with March up 0.25 cent or 0.2 percent at $1.5005 per lb.

Dealers said the market was underpinned by the threat to crops in Central America from roya or leaf rust but a favourable outlook for this year's harvest in top grower Brazil was helping to keep a lid on prices.

"Coffee has just been trading between 160 and 140 (cents a lb) since early December," Lathiere said.

"I am quite disappointed by the fact that there isn't more of an up movement due to these problems in Central America because in the past these kind of problems would push prices to the upside. We know there will be problem for high quality beans and the demand for this kind of product is still important."

Cocoa futures on ICE were little changed with the market hovering just above Monday's seven-month low.

March cocoa futures on ICE rose $3, or 0.1 percent, to $2,198 a tonne. The contract fell to $2,157 on Monday, the weakest level for the front month since June 2012.

Dealers said an improving outlook for crops in West Africa after a slow start to the season had helped to cap the upside potential for prices.

May cocoa on Liffe rose 3 pounds or 0.2 percent to 1,447 pounds a tonne.

Ivory Coast cocoa exporter SAF Cacao's processing facility will be closed for up to three months following a fire early on Wednesday, the company's CEO said.

(Reporting by Nigel Hunt; editing by James Jukwey and Keiron Henderson)