Standard & Poor’s Rating Services raised its outlook on BP PLC, citing an improving financial risk profile for the oil giant more than two years after the Gulf of Mexico oil spill.

S&P said Tuesday that BP’s outlook was revised to “Positive” from “Stable.” The company also affirmed its investment-grade “A/A-1” ratings on long- and short-term corporate credit.

BP, based in London, owned the Macondo well that exploded in April 2010 in the Gulf of Mexico. Eleven workers were killed and more than 200 million gallons of oil spilled into the water.

BP’s annual payments stemming from the oil spill likely will decline in 2012 and 2013, S&P said. In addition, asset sales and medium-term production growth should help improve credit metrics.

S&P said it could raise the rating by a notch in the next one to two years if BP’s credit measures continue to strengthen and are sustainable, it has a strong operating performance and returns to production growth in regions such as the U.S. and United Kingdom.

The ratings agency said the outlook could be lowered to stable if the remaining near-term cash payments related to the spill are more than the $20 billion S&P has estimated.

It also could lower the outlook if BP approves substantial increases to shareholder distributions before it has reduces debt through planned asset sales and completed most of the Gulf payments.

Shares of BP rose 20 cents to $41.55 in afternoon trading. The price has ranged between $33.62 and $48.34 in the past 52 weeks.