Standard & Poor's has downgraded its long-term sovereign credit ratings on Ukraine from B to B-, S&P has said in a press release.

The outlook remains negative.

The agency also lowered the long-term Ukraine national scale rating to uaBBB- from uaA-. At the same time, they affirmed the short-term ratings at B.

The downgrade reflects their view that the government's strategy is increasingly unlikely to secure sufficient foreign currency to meet its elevated external financing needs, S&P said.

The agency noted that in May 2013 they had warned that favourable conditions on international capital markets could prove fleeting and further accentuate Ukraine's external funding pressures. This was confirmed by the inversion of the government's yield curve (when the yield of short-term bonds exceeds that of long-term bonds) at the end of September 2013.

"The ratings are constrained by our view of political uncertainty, financial sector stress, and weak external liquidity. The ratings are supported by Ukraine's still relatively low, albeit rising, government debt burden and fairly diversified economy," S&P said in the press release.

On September 21, Moody's Investors Service downgraded Ukraine's government bond rating to Caa1 from B3 and placed the rating on review for possible further downgrade.