DUBAI, Oct 25 (Reuters) - Credit ratings agency Fitch Ratings indicated on Monday it could cut the ratings of all banks in Qatar, saying it was concerned over the sector"s increasing reliance on external funding and a recent rapid growth in assets. Fitch placed Doha Bank (DOBK.QA), Al Khalij Commercial Bank (KCBK.QA) Qatar Islamic Bank (QISB.QA) and Dukhan Bank on "ratings watch negative", meaning it sees a greater potential for a downgrade in their ratings. It also added Qatar National Bank (QNBK.QA), Commercial Bank (COMB.QA), Ahli Bank (AABQ.QA) and Qatar International Islamic Bank (QIIB.QA) on negative watch. The Qatari banks" reliance on "external funding, coupled with the large size of the banking system, could have moderately weakened the authorities" ability to support the banking sector," the ratings agency said in a statement. Foreign funding was $193 billion at the end of August, Fitch said, representing 48% of the Qatari banking sector"s liabilities compared with $121 billion and 38% at the end of 2018. Foreign assets were "broadly stable" and the banking sector"s net external debt was $133 billion, representing 82% of expected gross domestic product (GDP) this year, it said. Reporting by Hadeel Al Sayegh; Editing by Kirsten Donovan, Susan Fenton and Paul Simao