Kissinger's consulting firm announced his death in a statement, but did not give a cause.

Kissinger is an academic, politician and renowned diplomat who wielded unparalleled influence on U.S. foreign policy during the administrations of Presidents Richard M. Nixon and Gerald Ford. In the decades since, he has worked as a consultant and author, developing ideas that have influenced politics and business around the world.

The New York Times said that few diplomats have been both praised and lambasted as strongly as Kissinger. Considered the most powerful U.S. secretary of state since World War II, he was alternately praised as an extreme realist who reshaped diplomacy to reflect U.S. interests and condemned as abandoning American values because he believed it served U.S. purposes.

During the Nixon and Ford administrations, Kissinger wielded unusual influence in global affairs with his gruff, commanding demeanor and behind-the-scenes maneuvering of power, the Associated Press reported. He was both vilified and awarded the Nobel Peace Prize.

In the turmoil of Watergate, Kissinger's power grew, and he played a role akin to a "co-president" to a weakened Nixon.

Kissinger, who fled Nazi Germany as a young man, became one of the most influential and controversial foreign policy figures in U.S. history.

Kissinger is synonymous with American foreign policy in the 1970s. He won the Nobel Peace Prize for helping to arrange an end to U.S. military involvement in the Vietnam War and is credited with helping improve relations between China and the United States.

Kissinger played an important role in establishing diplomatic relations between the United States and China. In 1971, Kissinger, then the US President's Assistant for National Security Affairs, secretly visited China and joined hands with the Chinese side to facilitate President Nixon's "ice-breaking trip" to China in 1972, and realized the "handshake across the Pacific Ocean" that shook the world.