JAKARTA, May 20 (Reuters) - Indonesia unveiled a sweeping plan on Wednesday to centralise exports of key commodities ‌such as palm oil and coal, aiming to boost government revenue through tighter control of the sale and pricing of its abundant natural resources.

Sovereign wealth fund Danantara will oversee a trading company designated to channel exports, starting with palm oil, coal and ferroalloys after a three-month transition. The government may add more commodities at three-month intervals.

"I tell my ​cabinet, formulate prices for nickel, gold. Every price must be determined by us," President Prabowo Subianto said in a fiery speech to ​parliament.

"If they don't support our price, then they don't have to buy it. We can use it ourselves."

Indonesia is ⁠the world's biggest exporter of palm oil, thermal coal and nickel, and Prabowo's plan aims to tackle concerns about under-invoicing and how exporters account ​for transfer pricing.

INVESTOR WARINESS

Indonesia's moves to assert greater control over its resources have rattled investors.

Tighter nickel ore quotas, higher taxes and a new pricing formula ​are driving up costs and threatening investment, the China Chamber of Commerce in Indonesia warned Prabowo in a letter this month.

"Investors are increasingly concerned on policy direction, and this has driven outflows from Indonesia's capital markets," said Jayden Vantarakis, head of ASEAN research at Macquarie Capital in Singapore.

"It's hard to see how this announcement will change the direction," ​he said, adding that state-owned companies were already heavily involved in every key resource sector from energy to minerals such as copper, tin, nickel ​and gold.

GROWING PRESSURE

Economic pressure on Indonesia is mounting, with a series of ratings outlook downgrades and the rupiah currency repeatedly plumbing record lows against the U.S. dollar, as ‌Prabowo's ambitious ⁠spending plans fuel investor wariness.

Another new measure requires all exporters of natural resources to keep their entire export revenues in state-owned banks from June 1, in a step Senior Economic Minister Airlangga Hartarto said aims to stabilise the flagging rupiah.

The central bank also raised interest rates on Wednesday for the first time in two years, by a higher-than-expected 50 basis points.

Rumours about the plan spooked the market on Tuesday, stoking concerns it could bring changes in ​pricing mechanisms and squeeze trader margins. Jakarta's ​main stock index (.JKSE), opens new tab fell 0.82% ⁠on Wednesday, after a drop of 3.5% the previous day.