Gold, a traditional safe investment in troubled times, has hit a series of record high prices. The prices of most other commodities, including oil, fell as investors appeared to expect a slowdown that would cut demand for energy and materials.

U.S. President Barack Obama said he disagrees with the downgrade by the Standard and Poor’s rating agency. He says he hopes it will prompt lawmakers in Washington to agree on a plan to manage Washington’s debt and deficit that includes higher taxes for the wealthy and cuts in spending on social programs. Republicans immediately rejected any tax increases.

S&P Monday defended its decision, saying increasing debt levels in the United States and the inability of Congress and the president to reach political consensus for significant deficit reductions were “no longer comparable with the most highly rated governments.”

The other two major credit rating agencies – Moody’s and Fitch – have so far kept the U.S. at the highest rating.