HOUSTON (REUTERS) - A trading unit of Singapore-listed commodities firm Noble Group was this week awarded a tender launched by state-run oil firm Petroecuador to buy up to 3.12 million barrels of premium diesel, traders told Reuters on Thursday (Jan 7.

Noble Americas is a regular supplier to Ecuador, especially since in 2014 it signed a US$1 billion loan-for-oil agreement with Petroecuador that allows it to be chosen as preferred provider when matching the best offer submitted by other firms.

Noble, whose credit rating has been downgraded by Moody's and Standard & Poor's to junk due to concerns about the largest Asian commodity trader's liquidity, had won a previous diesel tender to sell 2.88 million barrels to Ecuador. Deliveries related to that offer started in November.

Analysts expect the downgrade to put more pressure on Noble, which has a total of $2.5 billion worth of loans due in 2016, according to data from Thomson Reuters LPC.

Noble won with an offer of US$1.57 per barrel over the price of ultra-low sulfur diesel (ULSD) at the U.S. Gulf Coast, the traders added.

First delivery of 240,000 barrels of premium diesel with up to 50 parts per million of sulfur must be made on Jan. 20-22 at Esmeraldas, La Libertad, Punta Arenas or Boca del Rosario ports, according to the tender's terms.

Firms PTT International, Glencore, BB Energy, Citizens Resources, Trafigura and Arkham also submitted bids.