The U.S. Federal Reserve (Fed) is planning to begin its fourth round of bank stress tests in the coming weeks, a senior Fed member said on Friday. \"We will conduct the annual supervisory stress tests ... in a couple of weeks,\" said Janet Yellen, vice chairman of the central bank, at a banking conference. \"Concerns about European fiscal and banking issues have contributed to strains in global financial markets that pose significant downside risks to the U.S. economic outlook,\" Yellen said. \"We are monitoring European developments very closely, and we will continue to do all that we can to mitigate the consequence of any adverse developments abroad on the U.S. financial system.\" As additional data are collected on significant credit exposures, Yellen said, stress tests may evolve into an effective way to \"identify linkages across systemically important institutions that could lead them to fall into financial distress at the same time.\" The Fed oversees Wall Street\'s biggest banks, including Citigroup, Bank of America, JPMorgan Chase & Co., and Wells Fargo. The Fed has performed periodic stress tests on the 19 banks it watches since 2009. Market reactions indicated that the previous stress tests on U. S. banking systems were constructive to stabilizing the confidence of the financial sector.