By JEFF ZELENY

WASHINGTON, Oct. 1 — Senator Barack Obama will propose on Tuesday setting a goal of eliminating all nuclear weapons in the world, saying the United States should greatly reduce its stockpiles to lower the threat of nuclear terrorism, aides say.

In a speech at DePaul University in Chicago, Mr. Obama will add his voice to a plan endorsed earlier this year by a bipartisan group of former government officials from the cold war era who say the United States must begin building a global consensus to reverse a reliance on nuclear weapons that have become “increasingly hazardous and decreasingly effective.”

Mr. Obama, according to details provided by his campaign Monday, also will call for pursuing vigorous diplomatic efforts aimed at a global ban on the development, production and deployment of intermediate-range missiles.

“In 2009, we will have a window of opportunity to renew our global leadership and bring our nation together,” Mr. Obama is planning to say, according to an excerpt of remarks provided by his aides. “If we don’t seize that moment, we may not get another.”

His speech was to come one day after an announcement by the Bush administration that it had tripled the rate of dismantling nuclear weapons over the last year, putting the United States on track to reducing its stockpile of weapons by half by 2012.

The exact number of weapons being dismantled, like the overall stockpile, is secret, but officials said Monday that with the planned reductions, the total number of American nuclear weapons would be at the lowest levels since Dwight D. Eisenhower was president.

Under a 2002 treaty, the United States and Russia agreed to limit the number of operational nuclear weapons in their arsenals to between 1,700 and 2,200 by 2012, though that agreement did not address weapons in reserve stockpiles.

Mr. Obama, Democrat of Illinois, is seeking to draw attention to his foreign policy views with the approach of the fifth anniversary of the Congressional vote authorizing military action in Iraq. He is highlighting his early opposition to the war, which he argues is a sign of judgment that is more important than the number of years served in Washington.

Mr. Obama, a member of the Foreign Relations Committee, often tells voters that the Iraq war has consumed American foreign policy to the detriment of its ability to address other threats facing the nation. In his speech on Tuesday, aides said, Mr. Obama will assert, as he has before, that the United States should not threaten terrorist training camps with nuclear weapons.

If elected, Mr. Obama plans to say, he will lead a global effort to secure nuclear weapons and material at vulnerable sites within four years. He also will pledge to end production of fissile material for weapons, agree not to build new weapons and remove any remaining nuclear weapons from hair-trigger alert.

In his speech, according to a campaign briefing paper, Mr. Obama also will call for using a combination of diplomacy and pressure to prevent Iran from acquiring nuclear weapons and to eliminate North Korea’s nuclear weapons programs. Aides did not say what Mr. Obama intended to do if diplomacy and sanctions failed.

In setting a goal of eliminating nuclear weapons in the world, Mr. Obama is endorsing a call for “urgent new actions” to prevent a new nuclear era that was laid out in January in a commentary in The Wall Street Journal written by several former government officials. The authors of the article were George P. Shultz, secretary of state in the Reagan administration; Henry Kissinger, secretary of state in the Nixon and Ford administrations; William J. Perry, secretary of defense in the Clinton administration; and Sam Nunn, a former chairman of the Senate Armed Services Committee.

David E. Sanger and Steven Lee Myers contributed reporting.