The official rate of the Russian ruble for tomorrow settlement fell by 40.21 kopecks against the dollar to 31.8180 after a strong increase in the previous trading session, the MICEX exchange said on Wednesday. The value of the bi-currency basket, comprising $0.55 and 0.45 euros, increased seven kopecks to 36.96 rubles as of 10:03 a.m. Moscow time. The index of the ruble-denominated MICEX stock exchange firmed 0.21 percent to 1,383.35, while the index of the dollar-denominated RTS stock exchange gained 0.10 percent to 1,371.34 as of 11:48 a.m. Moscow time. Aton analyst Yelena Kozhukhova said worries about Greece\'s sovereign default held back the growth of core Russian indices. \"But we are not ruling out the return of optimism to the markets during the day,\" she said. Asian markets showed mixed trends, while the price of Brent oil blend decreased one percent to $106 per barrel. In Europe, the FTSE100 fell 0.26 percent to 5,280.54, the DAX slipped 0.14 percent to 5,619.73, CAC40 decreased 0.18 percent to 3,017.42 as of 11:30 a.m. Moscow time