(Adds background, S&P comment)
Jan 28 Standard & Poor's cut its long- and short-term foreign currency sovereign credit ratings on Ukraine to "CCC+/C" from "B-/B", with a negative outlook, citing escalating political instability.
"We now assess Ukraine under our criteria as exhibiting characteristics of a 'distressed civil society with weakened political institutions,' diminishing the government's capacity to maintain timely debt service," S&P said on Tuesday.
"The outlook is negative, reflecting our view of the potential for a further reduction in the government's willingness or ability to service its debt, due to the evolving political situation," the ratings agency said.
Prime Minister Mykola Azarov resigned on Tuesday to try to calm violent protests in which six people have been killed.
S&P said that should the government of President Viktor Yanukovych fall, an expected financial support package from Russia would be less certain.
However, Russian President Vladimir Putin said his country would honor its pledge to lend Ukraine $15 billion and reduce the price of gas it supplies to its neighbor even if the opposition forms the next government.
The protests erupted after the government walked away in November from a free trade agreement with the European Union.
Azarov tendered his resignation as parliament met for an emergency session to work out a deal that would satisfy the opposition and end protests in the capital, Kiev.
(Reporting By Kanika Sikka in Bangalore; Editing by Maju Samuel)