Rising supply from top producer Thailand was weighing down physical prices, but Indonesian exporters were reluctant to lower their offers.
"It would be difficult to lower our offers considering raw material prices. SIR20 is already the cheapest available grade in the market," one Jakarta trader said.
October tyre-grade SIR20 was offered at 50.5 cents/lb, or $1.12 a kilogram, free-on-board (FOB) Plumbing/Begawan, from 51.5 cents/lb last week. November contract was offered at 50.75 cents/lb, while December was quoted slightly higher at 51 cents/lb.
Raw material supplies in Indonesia, the worlds number two producer and exporter, were relatively tight due to the wintering season in the southern part of Sumatra when falling leaves disrupt the flow of latex.
Rain also disrupted tapping. Prices edged higher at between 8,800 to 9,100 rupiah ($0.94 to $0.97) a kg, from 8,500 to 9,000 rupiah per kg in the previous week.
Traders also said Chinese buyers, whose presence is often cited as a bullish factor, purchased only small volumes from suppliers or dealers last week.
"The way the Chinese buy is discreet. They don't want to move the market so they buy in bits and pieces," said one Median trader.
Industry sources have said Indonesia's natural rubber output this year is expected to rise five to six percent from 1.792 million tonnes in 2003.