Reuters) - The United States will likely suffer the loss of its triple-A credit rating from another major rating agency by the end of this year due to concerns over the deficit, Bank of America Merrill Lynch forecasts. The trigger would be a likely failure by Congress to agree on a credible long-term plan to cut the U.S. deficit, the bank said in a research note published on Friday. A second downgrade -- either from Moody's or Fitch -- would follow Standard & Poor's downgrade in August on concerns about the government's budget deficit and rising debt burden. A second loss of the country's top credit rating would be an additional blow to the sluggish U.S. economy, Merrill said. "The credit rating agencies have strongly suggested that further rating cuts are likely if Congress does not come up with a credible long-run plan" to cut the deficit, Merrill's North American economist, Ethan Harris, wrote in the report. http://www.reuters.com/article/2011/10/23/us-usa-rating-merrill-idUSTRE79M2J120111023