At the same time, the organization affirmed the 'BB-' long-term foreign currency and 'BB' long-term local currency, 'B' short-term foreign and local currency sovereign credit ratings on the Republic, and 'trAA ' long-term and 'trA-1' short-term Turkish national scale ratings.
The 'BB ' transfer and convertibility assessment on Turkey was also affirmed.
"The deteriorating macroeconomic environment threatens to aggravate Turkey's external vulnerability and skew the risks to its fiscal and economic prospects to the downside," said Standard & Poor's credit analyst Farouk Soussa.
Soussa said in recent months, global liquidity conditions have been deteriorating, darkening Turkey's financing outlook, and heightened domestic political uncertainty significantly exacerbates this effect.
The analyst also said the increasingly challenging political and global environment that Turkey faces in the near term raises the likelihood of a prolonged deterioration in Turkey's financing conditions.
The ratings organization said the outlook will revert to stable if the government demonstrates that it can successfully manage the deterioration in the global economic environment and the political uncertainties it faces.