WASHINGTON, June 25 (Xinhua) -- Global warming would threaten the U.S. national security in 20 years by feeding illegal immigration, humanitarian disasters, political instabilities and terrorism, an intelligence official said on Wednesday.

    "We judge global climate change will have wide-ranging implications for U.S. national security interests over the next 20years," said Thomas Fingar, deputy director of National Intelligence for Analysis, when testifying before a joint House committee hearing, citing a report indicating the logic between the global warming and increasing recruits for terrorism.

    Fingar said that sub-Saharan Africa, the Middle East and Central and Southeast Asia are most easily hit by warming-related disasters including drought, flooding, severe weather and hunger, which could destabilize political situation in some countries and spark regional conflicts over natural resources.

    Although climate change alone would not overthrow any government in the next two decades, but its impact would exacerbate existing problems like poverty, social tension, environmental degradation and weakness of political institutions, he added.

    According to the report, National Intelligence Assessment, Africa is one of the most vulnerable regions, where increasing droughts could cut agricultural yields of rain-dependent crops by about half in the next 12 years.

    In Asia, between 120 million and 1.2 billion people would experience inadequate water supply and crops yields are likely to suffer 10 percent decline by 2025.

    However, Fingar noted that the influence of the efforts to curb global warming by changing energy policies on the U.S. national security interest may be even bigger than those of climate change itself.

    Congress requested last year to disclosed the "confidential" intelligence report, one of a series that include analysis of all 16 U.S. spy agencies on foreign policy, security and global economic issues.

    Democratic lawmakers criticized on Tuesday night the White House for having tried to "bury the future security realities of global warming."