Standard & Poor's has affirmed its long-term A- counterparty credit and insurer financial strength ratings on Sirius.
Standard & Poor's credit analyst Earl Lancaster said: "The A- ratings on Sirius reflect the company's robustness, coupled with its reduced ability to raise capital.
"Sirius is, however, not expected to need new capital in the foreseeable future."
The ratings agency said that the troubles at Sirius' parent company, ABB, have reduced its financial flexibility.
S&P added that strong prospective operating performance and its well-protected capital adequacy meant its A rating would remain.
A spokesman said: "Standard & Poor's considers Sirius to be exposed to a remote event risk, because failure to check the current financial troubles at ABB may ultimately result in decisions prejudicial to Sirius' business position."