In 1823, President James Monroe proclaimed the Monroe Doctrine, a policy regarding the political relationships of the United States and other countries of North America and South America. The doctrine warned European nations not to interfere with the affairs of the Americas. The Monroe Doctrine stated that any further colonization or interference by European powers in the Americas would be viewed as a hostile act toward the United States. The doctrine was significant in that it declared that the Western Hemisphere was off-limits to further colonization by European powers and played an important role in halting the spread of European imperialism in Latin America.