DUBAI - Commercial Bank of Qatar (CBQ) COMB.QA is in talks to sell its $217 million stake in Abu Dhabi-listed United Arab Bank UAB.AD , Qatar's third-largest lender said on Tuesday.Qatari companies are exiting the UAE, part of a group of Arab countries that cut off diplomatic and transport ties with Doha in June.The bank said it had entered into a 90-day period of exclusivity with a "third party purchaser" it did not name.Commercial Bank owns 40 percent of United Arab Bank and the stake is worth around $217 million, Thomson Reuters data showed.Commercial Bank CEO Joseph Abraham told Reuters on Monday that board meetings at United Arab Bank were now held by video conference because of travel restrictions imposed by the UAE.Saudi Arabia, the UAE, Egypt and Bahrain cut diplomatic and economic ties, accusing Qatar of supporting terrorism, a charge denied by Doha.Deposits in Qatari banks from the four Arab countries have been withdrawn and Qatari banks are no longer able to raise funding there.Last week Qatar Insurance QINS.QA said it would close its Abu Dhabi branch because it was not able to renew its business licence. United Arab Bank is listed in Abu Dhabi but headquartered in Sharjah.(Reporting by Saeed Azhar, editing by Louise Heavens and Jason Neely) Saeed.Azhar@thomsonreuters.com; +65-64035664 ; Reuters Messaging: saeed.azhar.reuters.com@reuters.net))