Vietnamese farmers held back from selling coffee beans this week due to low prices, traders said on Thursday, as trade remained sluggish in Asia's top coffee markets due to the holiday season.

Farmers in the Central Highlands, Vietnam's largest coffee-growing area, sold coffee at 33,600 dong ($1.45) per kg, flat from last week.

March robusta coffee settled up $7, or 0.5%, at $1,382 per tonne on December 31.

"Although farmers are under pressure to sell beans to cash in ahead of the Lunar New Year, which is three weeks away, unattractively low London prices have discouraged them," said a trader based in the region. "Farmers still hoped that prices would go up."

Vietnam's coffee exports in 2019 fell 13.9% from a year earlier, to about 1.61 million tonnes, official data showed.

Traders in Vietnam offered 5% black and broken grade 2 robusta at a $50 premium per tonne to the March contract on Thursday, compared with last week's $70-$80 premium.

Meanwhile, the Indonesian market resumed trading after being closed for holidays last week.

Indonesia's grade 4 defect 80 robusta beans were offered at premiums of $250 to the March contract this week, a trader in Sumatra's Lampung province said.

"Trade activity is still light because of the holidays," the trader said.

Indonesia exported 16,202 tonnes of robusta coffee beans from Lampung province in December, up 26% year-on-year, data from local trade office showed on Thursday.