Bank Indonesia held the rate at 7.5 percent, as expected. The last change was a cut of 25 basis points in February.

The rupiah is at a 17-year low -- the unit was changing hands at 13,839 to the dollar in Tuesday afternoon trade -- and has been sliding for months. It faced further pressure from China's yuan devaluation last week.

The weakening currency means the bank has little space to reduce rates, even after growth slowed to a six-year low of 4.67 percent in the second quarter.

A cut tends to boost growth but weigh on currencies.

"Bank Indonesia's focus in the short term is directed at steps to maintain the stability of the rupiah amid continuing global economic uncertainty," the central bank said in a statement after its monthly board of governors' meeting.

The bank added that the board has agreed to tighten rules on foreign currency purchases as part of measures aimed at stabilizing the rupiah.

Anyone who purchases foreign currencies worth more than US$25,000 per month must provide details to authorities, down from $100,000 a month previously, central bank governor Agus Martowardojo told reporters.

The central bank earlier this year revised down its full-year growth forecast for 2015 to between 5.0 and 5.4 percent, while the World Bank has forecast just 4.7 percent.

While the immediate pressure on the rupiah caused by China's devaluation has passed, economists said it would still be hard for Bank Indonesia to cut rates as expectations grow that the US Federal Reserve will soon tighten monetary policy.

The reason Indonesia cannot cut rates "ultimately boils down to its worry about central bank surprise of another sort '€“- that the Fed is still bent on hiking, possibly sooner than the market expects," said Wellian Wiranto, an economist from Singapore-based OCBC Bank.

"Until that is out of the way, it remains too risky."(+++)

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