Describing nuclear weapons as the most dangerous legacy of the Cold War, U.S. President Barack Obama Sunday said his administration would immediately and aggressively seek ratification of the Comprehensive Test Ban Treaty (CTBT), reports say.

Obama's comments came hours after North Korea Sunday successfully launched a long-range rocket mounted with a communications satellite.

Unveiling his non-proliferation agenda in Czech capital Prague, Obama said the U.S. has the moral responsibility to lead global efforts for a world free of nuclear weapons.

He announced that the U.S. would host a summit next year on Nuclear Security to develop global approaches to these global challenges, and to forge new partnerships to prevent the spread of nuclear weapons and to secure nuclear materials with the ultimate goal of reducing and eventually eliminating nuke weapons.

Stating that he was not naïve to think that this goal (of a nuclear-free world) will be reached quickly, perhaps not in his lifetime, he said, We cannot succeed in this endeavor alone, but we can lead it.

So today, I state clearly and with conviction America's commitment and desire to seek the peace and security of a world without nuclear weapons, he said.

The president said ratification of the treaty that the Senate rejected a decade ago is one of the concrete steps the U.S. can take to reach his goal of ridding the world of nuclear weapons.

To achieve a global ban on nuclear testing, the Obama administration will work to bring the CTBT into force, including Senate ratification of the Treaty, the White House said in a statement.

148 countries have already ratified the treaty, and it will enter into force once the U.S., China, India, Pakistan, Israel, Iran, Egypt, Indonesia and North Korea ratify it.

To combat the threat of nuclear weapons falling into the hands of terrorists, the statement said Obama would call for a new international effort to secure vulnerable nuclear materials around the world within four years.

Nuclear weapons or materials in the hands of al-Qaida or other terrorists is the most immediate and extreme threat to global security, the White House fact sheet said. To protect our people, we must act with a sense of purpose without delay.

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