Moody's Investors Service cut the outlook for Qatar's banking system to negative from stable on Tuesday amid a continuing blockade of the country by its neighbors.
Qatar has faced a two-month-long economic embargo imposed by a group of fellow Gulf Cooperation Council countries, including Saudi Arabia.
The Saudi-led group has presented Qatar with a list of demands, including shutting down the Al-Jazeera news network, the closure of a Turkish base and a downgrade of its relations with Iran. Qatar has refused.
Moody's pointed to weaker operating conditions and continued funding pressures for Qatar's banks.
"A prolonged regional dispute could trigger some outflows of foreign deposits and other external funding," Moody's said in a press release, noting that those funds accounted for around 36 percent of total system liabilities as of May.
Those potential outflows would reduce Qatari banks' liquidity buffers, with domestic deposits currently tight amid lower oil revenues, the ratings agency said.
Moody's said it was concerned about the banks' ability to access external funding.