It's "fair" to say that countries such as Oman and Bahrain are vulnerable to a potential rating downgrade if the coronavirus outbreak lasts longer than expected, according to the chair of sovereign ratings at a credit rating firm.

That's because the two countries have high fiscal breakeven oil prices, Frank Gill of S&P Global Ratings told CNBC's "Capital Connection" on Tuesday. Oil prices have been under pressure due to concerns about the economic impact of the coronavirus, with both Brent and U.S. crudes down more than 10% since the beginning of the year.

The Organization of the Petroleum Exporting Countries has slashed global oil demand growth forecasts as the coronavirus continues to spread. For China alone, OPEC revised its demand forecast down by 0.2 million barrels a day for the first half of 2020.

The first coronavirus infections surfaced in late 2019 in the Chinese city Wuhan, and the disease has since killed more than 2,000 people in China. After the Lunar New Year holiday in late January, many businesses in China extended their closures in a bid to control the virus situation.