CEDAR RAPIDS, Iowa — Republican presidential candidate John McCain said Thursday he would fire Securities and Exchange Chairman Christopher Cox if he were president, accusing the former GOP congressman of betraying the public's trust.

President Bush appointed Cox to lead the SEC in 2005. He had been a Republican congressman from California for 17 years and had served on House committees overseeing investor protection and U.S. capital markets.

Democratic presidential candidate Barack Obama had criticized McCain for responding to the financial turmoil on Wall Street by suggesting a high-level commission be established to study its causes. In his speech Thursday, McCain called for the creation of a trust to work with the private sector and regulators to identify institutions that are weak and to take measures to strengthen them.

"You can't wait any longer for more failures in our financial system," McCain said.

Stocks on Wall Street have tumbled this week amid the worst financial meltdown in the U.S. since the Great Depression.

An SEC spokesman didn't immediately return a telephone call seeking comment on McCain's statement.

The Securities and Exchange Commission oversees regulation of U.S. markets.