U.S. President Barack Obama and Russian President Dmitry Medvedev have agreed to sign a new treaty that will reduce and limit global stockpiles of nuclear weapons.

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Russian President Dmitry Medvedev and U.S. President Barack Obama, seen here in 2009, agreed Friday to sign a new nuclear arms limitation treaty in April. ((Mikhail Klimentyev/Reuters/RIA Novosti/Kremlin))

The "New START Treaty," a successor to the 1991 Treaty on the Reduction and Limitation of Strategic Offensive Arms, limits each country to 1,550 warheads, including intercontinental and submarine-launched ballistic missiles.

That's a 30 per cent reduction in the number of warheads permitted in an earlier agreement, the Moscow Treaty of 2002.

The new treaty, finally agreed to by Obama and Medvedev in a phone call Friday morning, includes a verification system that includes on-site inspections and data exchanges.  

Obama and Medvedev will sign the treaty in Prague on April 8.

The White House is hailing the treaty as a "landmark agreement [that] advances the security of both nations and reaffirms American and Russian leadership on behalf of nuclear security and global non-proliferation."

'[The treaty also] maintains the flexibility that we need to protect and advance our national security.' —U.S. President Barack Obama

It will also "reset" relations between the two countries, a focus of Obama since he took office in 2009.

"When the United States and Russia can co-operate effectively, it advances the mutual interests of our two nations, and the security and prosperity of the wider world," Obama said Friday.

"[The treaty also] maintains the flexibility that we need to protect and advance our national security, and to guarantee our unwavering commitment to the security of our allies," he said.

In Russia, Medvedev's spokeswoman, Natalya Timakova, told the Interfax news agency, "This treaty reflects the balance of interests of both nations."

The treaty cannot enter into force until it has been approved by the U.S. Senate and the Russian legislature.

No limits on defences, long-range missiles

The White House said the treaty does not contain any constraints on testing, development or deployment of current or planned missile defences. The U.S. has a missile defence system based mainly in the U.S., and it is planning one in Europe.

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U.S. President Barack Obama and Secretary of State Hillary Clinton announced the new treaty in Washington, D.C., on Friday. ((Charles Dharapak/Associated Press))

The treaty also does not impose limits on planned U.S. long-range non-nuclear missiles, the White House said.

Russia had sought to include limits on current and planned U.S. missile defences in the treaty.

U.S.  Secretary of State Hillary Rodham Clinton on Friday said the new treaty gives the U.S. and Russia more credibility as they prepare to attend an international meeting of leaders on nuclear proliferation in Washington next month.

Ratification of the treaty will require 67 votes, or two-thirds of the U.S. Senate. Clinton, asked whether such a margin could be achieved given the recent fierce partisan battles and close votes over health care, said it could.

"National security has always produced large bipartisan majorities, and I see no reason why this should be any different," she said. "The vast majority of senators will see that this is about America's national interest, it's not about politics."

With files from The Associated Press