Index compiler MSCI said it could rank Saudi Arabia as an emerging market alongside countries such as Brazil and China, if the oil-rich kingdom moves ahead with longstanding plans to open up its stock market to foreign investors.

That could vault Saudi Arabia above smaller regional markets such as the United Arab Emirates and Qatar, which MSCI continues to rate as "frontier" markets in its global market indexes. Inclusion in the MSCI emerging markets index tends to lead to a big inflow of investment from global stock market funds which track the index.