* But rates to remain firm on port congestion, strong demand
* Baltic capesize index hit 4-year high on Tuesday
* Strong Chinese demand for coal, iron ore help to drive rates
By Keith Wallis
SINGAPORE, Dec 14 (Reuters) - Freight rates for large dry cargo ships on key Asian routes could slip next week, although they are expected to remain close to three-year highs amid port congestion and a strong demand for iron ore and coal, brokers said.
"We might see rates take a breather and come off a bit," a Singapore-based dry cargo broker said on Thursday.
That came as cargo owners have largely covered their freight requirements for December, according to brokers and chartering data on the Reuters Eikon data.
Cargo futures, which price forward freight rates on a quarterly basis, dipped on Wednesday suggesting that shippers and cargo owners expect rates to slip early next year.
The Baltic Exchange index for large capesize ships .BACI fell 1.9 percent, or 82 points, on Wednesday after hitting a four-year high of 4,293 points on Tuesday. is equivalent to earnings of more than $30,000 per day, Norwegian ship broker Fearnley said.
"Vale VALE3.SA is still quiet. They have not fixed any vessels yet for January loading," the Singapore broker, who specialises in fixing cargo for 180,000 deadweight tonne (DWT) capesize vessels, said.
Capesize freight rates from Australia and China have still to pass the psychologically important $10 per tonne mark, after BHP Billiton (LON:BLT) BHP.AX fixed the 178,021 DWT Ocean Courtesy at that rate earlier this week, according to the broker and data on the Reuters Eikon terminal.
" Rio Tinto (LON:RIO) RIO.AX and operators picked off ships at rates of $9.95 and under. All the miners except Fortescue Metals FMG.AX were in the market this week," the broker said.
With that volume of activity it was difficult to see rates climbing above $10 a tonne, the broker added.
"Delays in Chinese ports and generally tight tonnage supply in the Atlantic is supporting stronger rates towards Christmas as well as for the beginning of the new year," Fearnley said in a note on Wednesday.
Strong Chinese demand for coal and especially iron ore - staple cargoes for capesize ships - have helped drive the current rally in rates, said Ralph Leszczynski, head of research at ship broker Banchero Costa told Reuters.
Capesize charter rates on the Western Australia-China route .BAWB rose to $9.93 a tonne on Wednesday from $9.75 a tonne last week. They hit $9.98 per tonne on Tuesday, the highest since April 2, 2014.
Freight rates from Brazil to China .BATB slipped to $20.36 per tonne on Wednesday, against $20.94 per tonne the same day last week. They hit $21.27 a tonne on Dec. 4, the highest since Nov. 12, 2014.
Panamax rates for a north Pacific round trip voyage .BPHJ climbed to $11,583 per day on Wednesday from $10,859 per day last Wednesday, the highest since Nov. 6, although there is talk of a softening trend, Fearnley said.
Rates in Asia for smaller supramax ships turned negative this week, slipping to about $10,500 per day from west coast of India to China, Fearnley said.