No new nuclear warheads

"The United States will not develop new nuclear warheads. Life Extension Programs (LEPs) will use only nuclear components based on previously tested designs, and will not support new military missions or provide for new military capabilities," said the new strategy, which differentiates with Bush-era pursuit of low-yield "bunker buster" nuclear bombs to be able penetrate buried targets.

The document also asserts that "The United States will not conduct nuclear testing, and will seek ratification and entry into force of the Comprehensive Nuclear Test Ban Treaty."

The CTBT bans all nuclear explosions in all environments, for military or civilian purposes. It was adopted by the United Nations General Assembly in September, 1996, but it has not yet entered into force because some signatory states, including the U. S., did not ratify it.

Fighting nuclear terrorism

Terrorist attacks with nuclear weapons or other weapons of mass destruction are "the most immediate and extreme threat to global security," Obama said in his landmark Prague speech in April 2009, promising to secure all vulnerable nuclear material around the world within four years.

This emphasis on fighting nuclear terrorism was also reflected in the new nuclear strategy.

"For the first time, the NPR places preventing nuclear proliferation and nuclear terrorism atop the U.S. nuclear agenda," said the document. "It renews the U.S. commitment to hold fully accountable any state, terrorist group, or other nonstate actor that supports or enables terrorist efforts to obtain or use weapons of mass destruction, whether by facilitating, financing, or providing expertise or safe haven for such efforts."

Analysts said that the Obama administration's position on nuclear terrorism as reflected in the strategy is going to be a scene-setter for the Nuclear Security Summit which takes place in Washington on April 12-13.