PRAGUE, April 5 (Xinhua) -- U.S. President Barack Obama said on Sunday that the U.S. missile defense system in the Czech Republic and Poland will go forward "as long as the threat from Iran persists."

    "As long as the threat from Iran persists, we will go forward with a missile defense system that is cost-effective and proven," said Obama in a speech to the Czech public in central Prague square. "If the Iranian threat is eliminated, we will have a stronger basis for security, and the driving force for missile defense construction in Europe will be removed."

    Obama said that Iran's "nuclear and ballistic missile activity "poses a real threat, not just to the United States, but to Iran's neighbors and Washington's allies.

    Obama reaffirmed his administration's readiness to "seek engagement with Iran based upon mutual interests and mutual respect."

    "We want Iran to take its rightful place in the community of nations, politically and economically. We will support Iran's right to peaceful nuclear energy with rigorous inspections. That is a path that the Islamic Republic can take. Or the government can choose increased isolation, international pressure, and a potential nuclear arms race in the region that will increase insecurity for all," he added.

    In the speech before his summit talks with EU leaders, Obama called for reducing nuclear arsenal and finally eliminating all nuclear threat in the world.

    "Existence of thousands of nuclear weapons is the dangerous legacy of the Cold War, and the world could be erased in a single flash of nuclear weapons," Obama said. "Today, the Cold War disappears ... but the threat of nuclear attack has gone up."

    He also noted that nuclear testing still continues and black trade of nuclear materials and technology still exists.

    "We must stand together for the right of people everywhere to live free of (nuclear) fear in the 21st century," Obama said.