* Robusta hits 8-month low as Vietnam harvest weighs
* Arabica touches lowest level since June 21
* Cocoa seen trading sideways
* Investors cautious ahead of U.S. presidential election
(Adds quote, updates prices)
LONDON, Nov 5 (Reuters) - Robusta coffee futures on Liffe fell to an eight-month low on Monday, while ICE arabica coffee also eased as a firm dollar contributed to weakness in soft commodity markets.
Sugar and cocoa futures on both ICE and Liffe were also slightly lower.
A range of dollar-priced commodities came under pressure as the dollar hit a two-month high against a basket of major currencies after job reports last week highlighted relatively solid U.S. economic fundamentals.
January robusta coffee futures were off $24 or 1.2 percent at $1,940 a tonne at 1459 GMT after earlier touching $1,935, the lowest level for the second-month since March 7.
Dealers said the market remained under pressure from the prospect of another large crop in top robusta producer Vietnam, where the harvest is underway.
``The market looks at it (the harvest) and they reckon the crop is going to be a quite substantial amount, and nobody wants to buy,'' said a London-based broker, noting that trading volumes were low as investors remained cautions ahead of the U.S. presidential election.
December arabica coffee futures were off 3.35 cents or 2.2 percent at $1.5135 per lb. The contract earlier hit $1.5115, the lowest level for the front month since June 21.
``I think it's a combination of speculative selling, and with the macro environment a little bit weaker as well, there is a bit of pressure coming from that direction,'' a UK-based broker said.
``The longer-term trend with the fundamentals where they are is still negative. I would expect we'll see that trend continue. We may well have a short-term pop or correction, but overall the market is going to continue to be under pressure,'' the broker added.
Speculators raised their net short position in ICE arabica futures for a fourth straight week in the week to Oct. 30, U.S. Commodity Futures Trading Commission data showed on Friday.
ICE December cocoa was off $15 or 0.6 percent at $2,434 per tonne.
Dealers said the market remained underpinned by a slow start to the harvest in Ghana, although in neighbouring Ivory Coast there appears to have been a smooth start to the main crop season despite major market reforms.
Cocoa arrivals at ports in top grower Ivory Coast reached around 142,000 tonnes by Nov. 4 since the start of the season on Oct. 3 exporters estimated on Monday, compared with 146,058 tonnes in the same period of the previous season.
``In the cocoa market there is limited impetus from either side. Production is slightly lower than last year, so there should be a limit to the downside but then there is weakness in key consuming region Europe, so there is weak demand and weak supply,'' said Tobias Merath, a commodities analyst at Credit Suisse, adding that cocoa was expected to trade sideways around $2,400 to $2,500 into next year.
ICE Futures U.S. said on Friday that certified cocoa stored in a Continental Terminals warehouse in New Jersey had been damaged by water following storm Sandy.
Benchmark Liffe March cocoa futures were down 1 pound or 0.1 percent at 1,577 pounds ($2,500) per tonne.
March sugar futures were off 0.16 cents or 0.8 percent at 19.29 cents a lb as the market continued to consolidate just above a six-week low set last week.
Dealers said the market was weighed down by ample supplies, with a substantial global surplus widely forecast in 2012/13.
The contract fell to 19.18 cents on Wednesday, the lowest level for the front month since Sept. 21.
Credit Suisse's Merath said prices could slip to 18 cents but were not expected to move much lower as sellers in top producer Brazil kept control of supply.
``There is a supply surplus, but they are not just dumping it on the market, they are gradually selling it, so from a fundamental view it is more like a neutral picture to us,'' Merath said.
Speculators lifted their net short position in raw sugar contracts on ICE Futures U.S. to a five-week high in the week to Oct. 30 as the futures market fell on plentiful supplies, U.S. Commodity Futures Trading Commission data showed on Friday.
December white sugar on Liffe was off $0.70 or 0.1 percent at $536.40 per tonne. ($1 = 0.6235 British pounds)
(Reporting by Nigel Hunt and Clare Hutchison; Editing by William Hardy and Jane Baird)