JAKARTA • Indonesia's long wait to win full investment-grade rank just got longer after S&P Global Ratings maintained its junk status because of weak fiscal performance.

S&P affirmed the country's BB+ rating on Wednesday, while leaving the door open for a future upgrade by maintaining a positive outlook.

It cited forecasts for larger budget deficits in coming years and a decline in corporate credit quality.

Fitch Ratings and Moody's Investors Service awarded Indonesia investment-grade status more than four years ago.

The failure to win to full investment-grade status may take the shine off Asia's best-performing bond market, with the nation's local currency notes gaining about 10 per cent this year, according to indexes compiled by Bloomberg.

The S&P report comes as government revenues fall short of targets because of weak tax collection and low commodity prices.

Mr Song Seng Wun, an economist at CIMB Private Banking, said: "Indonesia has done a bit more than in previous years to strengthen its fiscal position, but S&P may prefer to see a structural shift, leading to an actual improvement on the revenue collection front."

To improve revenue, the government is relying on a plan for a tax amnesty to lure funds stashed overseas, yet that Bill has been held up by Parliament.

Bank Indonesia said it will result in as much as 560 trillion rupiah (S$56 billion) being repatriated and help boost economic growth to as much as 5.4 per cent this year.

OCBC economist Wellian Wiranto said the S&P statement gives an impression that Indonesia's fuel subsidy reform is not thorough enough, with the government hesitant to allow domestic petrol prices to fully track international prices.

The nation's currency has strengthened 0.7 per cent against the US dollar in 2016, and the Jakarta Composite Index of shares is up 5.5 per cent.