Israel is now marking 60 years of democracy. For Israelis and their supporters overseas, it is a time of celebration. We reflect on the sacrifices that built the strongest self-government in the Middle East. More importantly, we will look ahead on how to protect this democracy for the next 60 years. Some leaders will focus on tactical moves in an uncertain peace process. Others will focus on short-range rockets raining down on Sderot. Still others will focus on the growing Hizbullah arsenal in Southern Lebanon. But as painful as these issues are, none poses an existential danger to Israel. Only one threat rises to this level - the growing danger from Iran. This danger is real and not based on the judgment of only Western intelligence agencies. Both the UN Security Council and the International Atomic Energy Agency (IAEA) found that Iran is in breach of its obligations under the UN Nuclear Non-Proliferation Treaty. Last May, the IAEA's director general, Mohammed El-Baradei, announced that Iran possesses the knowledge to enrich uranium to weapons-grade level. Almost a year later, Iran welcomed reporters to see its enrichment plant in defiance of no less than three UN Security Council resolutions. Iran's missile program is also expanding. Last November, the Iranians tested a new Ashura missile - an improved copy of a North Korean missile that Iran demonstrated can hit Israel. A month later, Iran tested new missiles using more advanced solid-fueled rocket motors similar to motors used by the United States and Russia. Lt. Gen. Henry Obering, the director of the US Missile Defense Agency, said Iran is developing these weapons at an accelerating pace, now ranking third behind Russia and China in flight tests. BEYOND IRAN'S growing arsenal, its president publicly displays a growing hostility towards Israel. A painful lesson of history teaches that dictators tell us what they will do before they do it. Mahmoud Ahmadinejad has made a number of statements pledging Israel's destruction - not just the infamous "wipe Israel off the map" remark. In 2005, he said of Israel that "very soon this stain of disgrace will vanish from the center of the Islamic world - and this is attainable." The following year, he said "like it or not, the Zionist regime is heading toward annihilation." He claimed "this regime will one day vanish" and then stated "the basic problem in the Islamic world is the existence of the Zionist regime, and the Islamic world and the region must mobilize to remove this problem." In a recent speech, he said "the Zionist regime is fraudulent and illegitimate and cannot survive." Ahmadinejad cannot be accused of hiding his intentions. He has been blatantly clear about his desire to destroy Israel - and UN agencies warn that his country is working to provide his military with such an option. Since president Harry Truman recognized Israel 11 minutes after it declared independence in 1947, America has provided critical bipartisan support to ensure her survival. When President George Bush and Congressional leaders mark Israel's 60th, there will be a narrow window to secure a permanent legacy of security against the new and growing danger. What will make the children of Israel's democracy safe in a new century? IN OUR view, the greatest birthday present would be something that builds a lasting legacy for the US-Israel relationship. In the Congress, we are circulating a bipartisan letter to President Bush asking him to put the full weight of the US ballistic missile defense behind our democratic ally Israel. With more than 60 Democrats and Republicans signing our letter, this commitment already carries bipartisan congressional support at high levels. In the 1990s, we jointly built a medium range defense system - the Arrow missile program - which intercepts missiles targeted at Israel. In 2001, the US granted Israel access to America's "Eyes in the Sky," giving added early warning to Israel in case of attack. Now we think we should take the next step and put the full weight of the US ballistic missile defense system behind the defense of our key ally. This system is already deploying to protect Japan and Western Europe. It should protect Israel as well. The US system reaches twice as far as Arrow and increases a defense engagement window by five times. Using its full capability, destruction of missiles aimed at Israel would happen hundreds of miles away from her borders. We urge President Bush and Prime Minister Olmert to make this defensive commitment a reality. By using the 60th birthday to announce that a US X-Band ground-based warning radar will be deployed to protect Israel, we can enhance Israel's security in the very near future. Linked to the US global system, Israel would have the full weight of Western defenses to protect her vulnerable cities. This commitment by the president and prime minister would also have a deterrent value - and send Iran the clear message that the only way to deal with Israel is to talk with her. This commitment could lower the security temperature in the Middle East. It would remind dictators of a painful lesson learned from World War II and the Cold War - that democracies are best when they stick together in defense of their values and citizens. While some may wish to make the Bush and Congressional visit about short-term tactical moves in an uncertain peace process, we hope our two great democracies can rise above week-to-week concerns and create the capability to stop Iran from carrying through on its heinous threats to destroy the homeland of those who survived the worst genocide in history and built a free and open democracy now entering its seventh decade. US Rep. Mark Kirk (R) represents the 10th district of Illinois. US Rep. Jane Harman (D) represents the 36th district of California.