CHRONOLOGY - Ups and downs of U.S.-Iran relations

(Reuters) - U.S. and Iranian officials attended a conference in Baghdad on Saturday aimed at stopping sectarian fighting in Iraq.

Here is a chronology of major events in Iran-U.S. relations:

August 1953 - CIA helps orchestrate the overthrow of Iran's popular Prime Minister Mohammed Mossadegh, restoring the Shah of Iran, Mohammed Reza Pahlavi, to power.

January 16, 1979 - Pahlavi is forced into exile after mounting discontent with his authoritarian rule.

-- February 1 - Ayatollah Ruhollah Khomeini triumphantly returns to Tehran after some 15 years in exile.

-- October - The U.S. allows the Shah to enter the country for medical treatment, angering the revolutionary government.

-- November 4 - Iranian students seize the U.S. embassy in Tehran and capture 90 hostages; 52 held captive for 444 days.

April 7, 1980 - U.S. President Jimmy Carter breaks off diplomatic relations with Iran.

-- April 25 - A U.S. commando mission to rescue the embassy hostages fails in the desert, killing eight Americans.