Standard & Poor's on Monday downgraded the outlook for the United States to negative, saying it believes there's a risk U.S. policymakers may not reach agreement on how to address the country's long-term fiscal pressures.

The S&P said the move signals there's at least a one-in-three likelihood that it could lower its long-term rating on the United States within two years.

The headline has enough of a shock value. The initial reaction is that this is negative for dollar assets across the board. said Lou Brien, a market strategist with DRW Trading in Chicago.

(Editing by James Dalgleish)