SOFTS-Liffe robustas hit five-month peak, sugar also higher

* Robustas supported by lack of sales by Vietnam farmers

* Speculators trim huge net short in ICE raw sugar

* Favourable mid-crop outlook limits upside for cocoa

(Adds quotes, updates prices)

LONDON, March 11 (Reuters) - Robusta coffee futures on Liffe rose to a five-month high on Monday buoyed by concern about dry weather in Vietnam and strengthening differentials in the world's top producer.

Sugar and cocoa prices on ICE were also higher.

Robusta coffee futures had risen about 14 percent so far this year, boosted by a combination of strong demand and concern that the 2013/14 crop in Vietnam could fall significantly due to dry weather.

Andrea Thompson, analyst with CoffeeNetwork, part of INTL FCStone, said the crop in Vietnam still had time to recover.

"If you get a normal May-October wet season (in Vietnam), I think you are going to be looking at a normal crop in 13/14 but clearly the market is being supported by it (dry weather) at the minute," Thompson said.

Differentials in Vietnam have also strengthened with farmers holding back sales in expectation that prices may rise further.

Coffee prices in Vietnam rose more than 3 percent from late last week to 45,500 dong ($2.17) per kg on Monday, the highest since September 2011 and almost on a par with London's futures prices, traders said.

"Farmers are not selling much, as they believe prices could go further, while their stocks are high," said a trader based in Buon Ma Thuot, the capital of Daklak.

May robusta coffee futures on Liffe rose $14, or 0.6 percent, to $2,195 a tonne by 1536 GMT after earlier touching $2,198, the highest level for the benchmark second month since October 2012.

Arabica coffee futures on ICE have, in contrast to robustas, fallen slightly this year with the market weighed by the prospect of a comparatively large "off-year" crop in top producer Brazil in 2013/14.

"It is going to be difficult for arabica to move significantly higher," Thompson said, noting favourable crop prospects in Brazil for 2013/14 and very early indications there could be a huge 2014/15 "on-year" crop.

Brazil's arabica coffee crop follows a biennial cycle but the gap between on- and off-year crops has been narrowing.

ICE May arabica coffee was up a marginal 0.20 cent or 0.1 percent at $1.4425 per lb.

REBOUND EXTENDED

Raw sugar futures were slightly higher as the market extended its rebound from a multi-year low set less than two weeks ago with speculators scaling back a huge net short position linked to excess global supplies.

Speculators trimmed their net short, or bearish, sugar positions in futures and options contracts on ICE Futures U.S. to their lowest level in a month during the week ended March 5, U.S. Commodity Futures Trading Commission data showed on Friday.

Dealers said the decline in the net short position was, however, smaller than many had expected and the market remained susceptible to short covering rallies.

"While the upside to sugar prices likely remains limited unless weather conditions prove detrimental in the Northern Hemisphere later this year, near record short net speculative positioning could exacerbate any weather-induced rally," Goldman Sachs said in a market note.

May raw sugar futures rose 0.07 cent or 0.2 percent to 18.78 cents a lb. The front month slumped to 17.61 cents on Feb. 28, its lowest level since August 2010.

Analyst Luke Mathews of Commonwealth Bank of Australia said the current advance was unlikely to be sustained, noting significant selling pressure around 19 cents.

"All prior short covering rallies over the past six months have proved temporary," he said in a market note, adding the bearish fundamental outlook had not changed.

May white sugar on Liffe was up $1.10 or 0.2 percent to $535.20 a tonne.

Cocoa futures were higher although the upside remained limited by favourable prospects for upcoming 2012/13 mid-crops in West Africa.

Abundant rainfall and sunshine across most of Ivory Coast's cocoa growing regions last week provided a boost for development of the April-to-September mid-crop, but harvesting could start late in some areas, farmers and analysts said on Monday.

"Confirmation of a benign 2012/13 outlook and still-elevated net speculative length suggest that prices may continue to decline in coming month," Goldman Sachs said.

Speculators raised a net long position in cocoa futures and options on NYSE Liffe in the week to March 5, exchange data showed on Monday.

May cocoa futures on ICE were up $19 or 0.9 percent at $2,139 a tonne while May cocoa on Liffe rose 10 pounds or 0.7 percent to 1,451 pounds a tonne.

(Reporting by Nigel Hunt; editing by Alison Birrane and Jason Neely)