WASHINGTON - Influential political scientist and former Harvard professor Samuel Phillips Huntington has died aged 81, the university reported on its website.

Huntington, who retired from active teaching at Harvard in 2007, died Wednesday at Martha's Vineyard in Massachusetts, the website said Saturday.

He was best known for his views on the so-called clash of civilizations. Huntington argued that conflicts in our post-Cold War world would be rooted in cultural and religious differences among major civilizations, rather than ideological rifts between nations.

He identified these major civilizations as Western (including the US and Europe), Latin American, Islamic, African, Orthodox (with Russia as a core state), Hindu, Japanese and 'Sinic' (including China, Korea and Vietnam).

He first made the argument in a 1993 article for the journal, Foreign Affairs. In 1996, he took it further in his book 'The Clash of Civilizations' and the 'Remaking of World Order'.

Huntington's work was often controversial. His latest book, published in 2004 and entitled 'Who Are We? The Challenges of America's National Identity' dealt with immigration and cultural identity. He was criticized for his observations that the most serious threat to US identity came from Mexican immigration, which was effectively splitting the nation in two.

Huntington was born April 18, 1927 in New York City. He received his bachelor's degree from Yale University in 1946. He served in the army and returned to the University of Chicago for a master's, next receiving a PhD from Harvard in 1951.

He is survived by his wife of 51 years, Nancy Arkelyan Huntington, two sons and four grandchildren. Huntington is to be buried in Martha's Vineyard, where he spent the last 40 summers.