Indonesia's robusta grade 4, 80 defects  COFID-G4-USD were traded at a $30 discount per tonne to the July contract, traders in Lampung said, compared with a $40 discount last week.

"Many exporters are scrambling to get coffee," said a trader in Lampung.

In Vietnam, the world's top robusta producers, the 5 percent black and broken grade 2 robusta  COFVN-G25-SAI was quoted at $20-$30 premium per tonne to London's ICE September contract  LRCU7, compared with a $20 premium a week earlier.

Vietnamese farmers quoted local prices  COFVN-DAK at 44,000-45,000 dong ($1.94-$1.98) per kg, compared with 44,000-44,200 dong a week ago, which traders said made export quotes higher than import offers.

Vietnam customs said on Thursday the country exported 122,000 tonnes (2.03 million 60-kg bags) of coffee in May, down 9.4 percent from a month earlier, and slightly above the government estimate of 120,000 tonnes.

Traders expected Vietnam's coffee exports to reach 90,000-120,000 tonnes in June while the U.S. Department of Agriculture forecast Vietnam's 2017/2018 harvest to increase 10 percent annually to 28.6 million bags of coffee, or 1.72 million tonnes, due to favourable weather in the first half of the year.