President Barack Obama said Wednesday that the threat of nuclear weapons has posed the "greatest danger" to the United States, warning "growing consequences" on Pyongyang and Tehran over their nuclear ambitions.

In his first State of the Union address delivered Wednesday night in U.S. Congress, President Obama said the greatest danger facing the United States is the threat of nuclear weapons, adding that the administration has been pursuing a world without nuke.

According to the president, at the Nuclear Security Summit, which is scheduled in April in Washington, the United States and other participants will claim a clear goal: "securing all vulnerable nuclear materials around the world in four years, so that they never fall into the hands of terrorists."

Obama told U.S. lawmakers, cabinet ministers, Supreme Court justices, top army officers and foreign diplomats that the administration has been exerting diplomatic efforts to deal with "those nations that insist on violating international agreements in pursuit of these weapons."

"That is why North Korea (the Democratic People's Republic of Korea) now faces increased isolation, and stronger sanctions -- sanctions that are being vigorously enforced. That is why the international community is more united, and the Islamic Republic of Iran is more isolated," said the president.

Nuclear stalemates on the the DPRK and Iran have been widely viewed by critics as major frustration to the Obama administration's foreign policy in its fist year.

In 2009, Pyongyang announced quitting from the Six-Party talks and conducted its second nuclear weapon experiment.

In order to break the stalemate in the Korean Peninsula's denuclearization, Obama sent his special representative to Pyongyang in an attempt to persuade the DPRK to return to the Six-Party talks, which also involve China, South Korea, Japan and Russia.

For Iran, since it took office in January, the Obama administration has been trying to persuade Tehran to abandon its controversial nuclear plan through the so-called engagement policy and the so-called P5+1 mechanism involving five permanent UN Security Council members -- the United States, Russia, China, France, Britain -- and Germany).

However, following months of interaction, the administration has admitted that its efforts have produced "very little in terms of any kind of a positive response" from Iran, warning to take the "second track" to bring the international community together to make Iranian leaders realize the "importance of changing their actions and decisions concerning their nuclear program."