Ahmadinejad made the comment at a news conference in the United Arab Emirates.
Iran is in a standoff with the UN Security Council over its nuclear program, which U.S. officials suggest is a covert attempt to possess nuclear weapons.
Ahmadinejad also said Persian Gulf countries should "get rid of" foreign troops, which he blamed for regional insecurity.
Tensions have been high between Washington and Tehran since late 2001, when they appeared to cooperate to usher in a post-Taliban government in Kabul, with U.S. President George W. Bush describing Iran as a member -- with North Korea and Iraq under Saddam Hussein -- of an "axis of evil" in his January 2002 State of the Union address.
Allegations have largely focused on Iran's ongoing nuclear program and actions in neighboring Iraq since the U.S.-led invasion to oust Hussein in 2003.
Sniping increased with the rise to the presidency in 2005 of former hard-line Tehran Mayor Ahmadinejad, who has repeatedly accused Western "enemies" of opposing Iranian development and fiercely defended Tehran's right to nuclear activities.
The United States and Iran have not had formal diplomatic relations since the storming of the U.S. Embassy in Tehran in 1979.
Continuing insurgent violence in Iraq has led to pressure in Washington for dialogue with Iran and with Syria in an effort to increase stability.
(AFP, AP, Reuters)