After two years of study, a panel of top scientists and military experts working for the National Research Council has concluded that the nation’s protections against missile attacks suffer from major shortcomings, leaving the United States vulnerable to some kinds of long-range strikes.

In a report, the panel suggested that President Obama shift course by expanding a system he inherited from President George W. Bush and by setting aside the final part of an antimissile strategy he unveiled in 2009. In so doing, the panel said, the president could set up the nation’s defenses to better defeat the kinds of long-range missiles that Iran may be developing.

It is the first time that the research council, an arm of the National Academy of Sciences, has weighed in on the nation’s overall plans for defeating missile attacks.

Chartered by Congress to give scientific and technical advice to the government, the council is considered to be the nation’s preeminent group of scientists. The 16-person panel consists of scientists, engineers and weapons experts from universities, research groups and national laboratories, including one in Livermore, Calif., that deals with nuclear arms.