UPDATE 1-General "90-pct-plus" sure on US missile defense

(Adds expert comment, House Armed Services staff statement)

By Jim Wolf

WASHINGTON, June 16 (Reuters) - U.S. ground-based interceptor missiles stand a better-than-90-percent chance of thwarting a "rogue nation" ballistic missile attack on the United States in the next five years, the second highest-ranking military officer told Congress on Tuesday.

Giving the most bullish military assessment to date on the Boeing Co (BA.N)-managed system's capabilities, Marine Corps Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, replied "ninety percent plus" when asked the odds of defeating a long-range missile that could be fired by North Korea.

Lisbeth Gronlund, an expert on missile defense at the Union of Concerned Scientists in Cambridge, Massachusetts, dismissed his estimate as "irresponsible and based on wishful thinking," not facts.

Cartwright was responding to a question from Senate Armed Services Committee member Evan Bayh, an Indiana Democrat, about what he would tell President Barack Obama about U.S. capabilities against long-range missile attack.

In follow-up remarks, he said his confidence reflected the limited threat foreseeable for the next two to five years from countries like North Korea and Iran, including the number of missiles they could fire in a "salvo."

By contrast, Charles McQueary, who retired as the Pentagon's top independent testing official last month, said in a report in December that flight testing of the so-called Ground-based Midcourse Defense, or GMD, "to date will not support a high degree of confidence in its limited capabilities."

Chicago-based Boeing is the prime contractor for the GMD system, which President Barack Obama wants to cap for now at 30 interceptor missiles in underground silos in Alaska and California cued by satellites, radar stations and other sensors.