Farmers in the Vietnam sold coffee at 33,800-34,000 dong ($1.46) per kg <COFVN-DAK> on Thursday, up from 32,600-33,500 dong a week earlier.

"Many domestic traders are increasing their purchases of the newly harvested beans, giving an upward push to domestic prices," a trader based in Dak Lak province said.

The trader said the speculation followed clearer forecasts that output would fall by 15-20 percent during the 2018-19 crop year, mostly due to unfavourable weather conditions.

"Now that the harvest is about to end, a forecast about a drop in output appears to have become true," said a second Dak Lak-based trader.

Vietnam is the world largest robusta producer. Farmers have picked nearly 85 percent of the 2018-19 harvest, which is expected to end mid-January.

Traders in Vietnam offered 5 percent black and broken grade 2 robusta <COFVN-G25-SAI> at a $30-$50 per tonne discount to the March contract, compared with a $40-$50 discount last week.

In Indonesia, no trade was recorded this week due to a holiday.

Grade 4 defect 80 robusta <COFID-G4-USD> was at a premium of $20-$30 to the March contract, unchanged from last week, a trader in the province of Lampung said.

Another trader in the province said Indonesian robusta was offered with $50 premium.