The respective short-term rating is at ‘B', while the transfer and convertibility assessment remains at ‘BB'.
S&P said PNG's economic output would be boosted by "as much as 20%" because of Exxon Mobil's new integrated LNG plant, and that "robust economic growth would continue" after the PNG LNG project reaches full production capacity this year.
Its contribution to PNG's economy would "enable the unwinding of PNG's related imbalances in the next few years".
Near-term political stability under Prime Minister Peter O'Neill's leadership will provide a "supportive environment" to manage economic and public expectations, with the government increasing spending to tackle development priorities and support growth.
However, the agency said urban crime and weak institutions were discouraging investors from participating in PNG's economy and that there were "gaps and lags" in economic data, and a lack of transparency in public-sector fiscal affairs.