The deadly suicide attacks on America two weeks ago have unleashed a torrent of debate about how best to combat terrorism, and that debate has spilled over to the question of whether or not the U.S. should build a national missile defense (NMD) system. 

While some say the terrorist methods revealed the limitations of developing a ballistic missile shield to protect the U.S. and its allies and interests, others say it is now more essential than ever.

"I think that this attack strengthens both the case of supporters of missile defense and opponents of missile defense," explained Michael E. O’Hanlon, a foreign policy scholar at the Brookings Institution in Washington, D.C.

"The supporters will say you never know where the next threat will come from and we have to protect ourselves from all threats," he said. "Opponents of excessive missile defense will say that missiles are not really the threat, we have to worry about the smaller and more devious types of threats."

But supporters of missile defense feel they have been presented with an unusual opportunity now to make the case for a broad and significant increase in defenses, including NMD.

"It is the need to create a seamless defense – from homeland defense to cyber defense," said James P. Pinkerton, who on behalf of the New America Foundation hosted a Capitol Hill discussion on missile defense this week.

"There is no isolation from these threats and we need to take them on as widely as possible," he said.

Rep. Rob Andrews, D-N.J., said it is a "sad and chilling reality" that the U.S. must expect that the terror isn’t over. "This was the worst day in the history of the United States, thus far. Thus far."

He said it would be "grave irresponsibility" on the part of the United States if it did not expect actions from rogue nations with weapons of mass destruction, including long-range missiles.

"If they have the opportunity to use it, one of those weapons will be ballistic missiles," he said.

And Rep. Mark Kirk, R-Ill., a Naval reserve officer who served in the Middle East and Balkans during several post-Desert Storm operations, says the U.S. today has no protection from such missile threats. Kirk, who was also at the New America Foundation forum, supports a "multilateral" approach involving heightened intelligence, diplomacy and missile defense.

But Michele Flournoy, military response expert for the Center for Strategic and International Studies, hopes to see a debate over "what relative priority [missile defense] should be given in that there will be a lot of other programs competing for dollars."

She said President Clinton had a more measured budget plan for developing a missile defense program, whereas Bush seems to have a more accelerated, "crash" approach.

"My own feeling is that we should sustain the program, but again, I would take the difference between" the Clinton approach and the Bush approach. "I would apply it to more immediate security concerns" and "reallocate the resources at the margins," she said, arguing that America feels more keenly the threat of other nonconventional threats. "I think there are some things that I would see as more urgent."

Several opponents of developing a missile defense system argue that the Russians -- who have the largest stockpile of nuclear weapons next to the U.S. -- won’t accept any attempt to break the 1972 Anti-Ballistic Missile Treaty that prohibits the development of missile defenses. But Kirk believes the attacks on Sept. 11 have changed the landscape.

"Russia will be facing the rogue nation threat as much as we do," he said. "I think the Russians are going to junk the ABM treaty themselves."

In addition to the Russians, many in the European community had expressed reservations and in some instances hostility to President Bush’s efforts to pursue missile defenses, arguing that besides breaking the ABM Treaty, building NMD may provoke unfriendly nations to launch a strike before a defense is developed. They also stress their belief that any system is not likely to work anyway.

But Andrews agrees that the events of two weeks ago have changed the climate and terms of debate. "I think we will have to divide the world between [Sept. 10] and [Sept. 11]. The world changed," he said. He believes the opinions of European allies and members of the Northern Atlantic Treaty Organization might change as well.

O’Hanlon suggested how much money Congress ultimately puts into the defense budget to cover Bush’s $8.3 billion request for a National Missile Defense program next year and the years beyond will reflect where the debate is heading.

"I think the [opponents’] argument is strengthened a little more by this terrible tragedy insofar as we should not fund missile defense at the expense of other homeland security," O'Hanlon said.

Last week, the Senate passed a budget with no cuts to missile defense as Senate Democrats relented in their opposition to the amount of the president’s request for funds for NMD. Some Senate members encouraged the president to use some of those funds for homeland counter-terrorism instead.

And on Tuesday, the House approved 398-17 a $343 billion defense bill, which included a small bipartisan cut to the president’s missile defense request.