Vietnamese coffee exporters have delayed loading part of contracts totaling around 100,000 tons since May because of a shortage of stocks, an industry official said on Monday.
This prompted at least two traders to raise concerns of possible defaults in shipments.
The thin stocks in Vietnam, the world's second-largest producer, coupled with an International Coffee Organization (ICO) forecast of a fall in global output in the next 2011/2012 crop, could support prices, which eased as fears about Greece's debt crisis eroded risk appetite and pressured the euro .
Liffe September robustas were down $30, or 1.28 percent, at $2,312 a ton at 0958 GMT.
"Coffee supply has been scant in Vietnam and exporters may have to buy more from foreign firms to meet the loading demand," Deputy Chairman Do Ha Nam of the Vietnam Coffee and Cocoa Association (Vicofa) said.
Exporters have so far bought back 10,000 tons from a foreign trading house which has established a warehouse in Vietnam, he added.
Parts of the 100,000 tons had been due for loading last month, but the volume include beans due to load from June and in the near future, Nam said by telephone, without giving further shipment details.
"The volume is likely that for contracts due for deliveries between May and the end of this crop year," a Vietnamese trader at a foreign company in Ho Chi Minh City said, when asked to comment on Nam's assessment.
"Delays have been popular now and given the current situation, if exporters continue to fail to secure beans and if they cannot stand domestic prices staying above export prices, defaults may emerge," he said.
A trader in Buon Ma Thuot, the capital of Daklak, said exporters may have to buy Vietnamese beans grade 2 now from foreign trading firms at a premium of $40 a ton and they could resell at a premium of $60 to London's September.
"The bean shortage is real and the problem may worsen in September or October with no stocks left," he said.
On Monday, Vietnamese robusta grade 2, 5 percent black and broken stood at around $2,400 a ton, free-on-board basis, based on a domestic price of 48.6 million dong ($2,357) per ton in the key growing province of Daklak.
Prices in Vietnam, which closely track London robusta futures markets, have eased from $2,511-$2,521 a ton last Tuesday.
Vietnam's coffee exports in June could drop to between 65,000 tons and 80,000 tons, or 1.08 million and 1.33 million bags, from 110,000 tons in estimated shipments last month, traders have said.
The volume of 100,000 tons, or 1.67 million 60-kg bags, represents 9 percent of the Southeast Asian country's output in the ongoing 2010/2011 crop year, based on the ICO's latest estimate of 18.5 million bags.
But foreign traders have forecast a higher output in Vietnam, ranging between 20 million and 22 million bags.
Premiums for robusta coffee widened further in Asia, with the value of Indonesian beans at its highest in more than a year on a combination of bad harvests, declining supply and purchases from domestic roasters, dealers said last Thursday.