Dec 21 (Reuters) - Most major stock markets in the Gulf ended lower on Tuesday, as investors worried over surging cases of the Omicron coronavirus variant. As Omicron remains the biggest cause for investor caution, economic growth forecasts are being reviewed lower, Farah Mourad, senior market analyst of XTB MENA, said. In Abu Dhabi, the index (.ADI) dropped 1.2%, dragged down by a 5% fall in telecoms firm Etisalat (ETISALAT.AD) and a 0.5% decrease in the country"s largest lender First Abu Dhabi Bank (FAB.AD). Dubai"s main share index (.DFMGI) edged down 0.1%, hit by a 3.2% fall in Emirates NBD Bank (ENBD.DU). The Central Bank of the United Arab Emirates said on Monday it would use new criteria to supervise banks" exposure to real estate, a crucial contributor the Gulf state"s economy that has been sluggish for years. read more The regulator will give banks one year to enhance their practices to meet the requirements, starting from Dec. 30. The Qatari index (.QSI) eased 0.1%, with sharia-compliant lender Masraf Al Rayan (MARK.QA) losing 0.5%. Separately, Qatar plans to invest at least $10 billion in U.S. ports and has approached international banks for financing, three finance sources said. read more Saudi Arabia"s benchmark index (.TASI) gained 0.8%, with Al Rajhi Bank (1120.SE) closing 1.6% higher and Saudi National Bank (1180.SE), the Gulf"s largest lender, rising 1%. Oil prices rebounded after a sharp fall in the previous session, although the market was still cautious because of the rapid spread of Omicron. Compliance by the OPEC+ group of producers with oil production cuts rose to 117% in November from 116% a month earlier, two sources from the group told Reuters, indicating output levels remain well below agreed targets. read more Outside the Gulf, Egypt"s blue-chip index (.EGX30) added 0.4%, with Talaat Mostafa Group Holding (TMGH.CA) gaining 2%. SAUDI ARABIA (.TASI) added 0.8% to 11,261 ABU DHABI (.ADI) dropped 1.2% to 8,459 DUBAI (.DFMGI) fell 0.1% to 3,152 QATAR (.QSI) eased 0.1% to 10,118 EGYPT (.EGX30) rose 0.4% to 11,525 BAHRAIN (.BAX) lost 0.1% to 1,770 OMAN (.MSX30) rose 0.6% to 4,075 KUWAIT (.BKP) added 0.9% to 7,590 Reporting by Ateeq Shariff in Bengaluru; editing by Barbara Lewis