The treaty, known as the NPT and which went into effect in 1970, seems flawed if not outright ineffective ahead of the conference at the United Nations.

Since the treaty was signed the world faces a new era of "rogue" states, international nuclear smuggling rings, and trans-national terrorist groups seeking weapons of mass destruction.

"The world has changed but the regime has not changed with it," the Washington-based Carnegie Endowment for International Peace said in a recent study.

Events over the past few days have shown how critical the situation is.

The United States reported that a short-range missile was fired early Sunday from the east coast of North Korea. It flew about 100 kilometersmiles) until it fell into the Sea of Japan, White House Chief of Staff Andrew Card told CNN.

US State Department spokesman Kurtis Coope said: "We have long been concerned about North Korea's missile program and activities and urge North Korea to continue its moratorium on ballistic missile tests."

North Korea shocked the world in August 1998 by firing a long-range missile over Japan that landed in the Pacific Ocean.

On Thursday, US Defense Intelligence Agency director Vice Admiral Lowell Jacoby told US lawmakers that North Korea is believed capable of arming a long-range missile that could reach the United States with a nuclear warhead.

North Korea is currently free of international surveillance of its nuclear activities. It kicked out International Atomic Energy Agency (IAEA) inspectors in December 2002, withdrew from the NPT the following month and now claims to have made atomic bombs.

Iran is showing the strains in the non-proliferation treaty in another way as the United States claims the Islamic Republic is secretly developing atomic weapons under the cover of a civilian nuclear power program that is under IAEA safeguards.

Iran's supreme leader, Ayatollah Ali Khamenei, on Sunday dismissed Washington's concerns over Tehran's nuclear program, the day after Iran said it was unhappy with the progress of nuclear negotiations with Britain, France and Germany, and warned it may resume uranium conversion activities in defiance of a November agreement.

The European Union, backed by the United States, wants Iran to halt all nuclear fuel cycle activities. In return, the EU is offering in talks that began in December a package of trade, security and technology incentives.

Iran has said repeatedly that its current enrichment suspension is temporary and voluntary, as it insists on its right under the NPT to conduct nuclear activities for peaceful purposes.

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