U.S. President Barack Obama (L) and his Russian counterpart Dmitry Medvedev sign a landmark nuclear arms reduction treaty in Prague, capital of Czech Republic on April 8, 2010. [Xinhua]

U.S. President Barack Obama and Russian President Dmitry Medvedev signed a landmark nuclear arms treaty Thursday, committing to significant reductions in their countries' atomic arsenals.

The pact, dubbed the "New START", was signed at Prague Castle, the seat of Czech presidency. At a new conference following the signing, Obama hailed the "historic" treaty as one step toward the realization of his dream of a nuclear-free world, which he outlined during a speech in Prague on April 5 last year.

Obama said that while a world without nuclear arms was a "long-term goal and may not be achieved in my lifetime," the pursuit of the goal will "make the United States and the world safer and secure."

The U.S. president said the treaty will help "reset" U.S.-Russia relations and boost cooperation and mutual respect, which has been a top American priority since he took office last year.

"When the United States and Russia are not able to work together on big issues, it is not good for either our nations or good for the world, " Obama said, adding the treaty is an important milestone for nuclear security in the world and in U.S.-Russian relations.

Medvedev told reporters he was satisfied with the treaty, which was "win-win situation" for the U.S. and Russia.

Once ratified by the U.S. Senate and the Russian Duma, the treaty, tenaciously negotiated by even the leaders themselves, will replace the 1991 Strategic Arms Reduction Treaty (START) that expired Dec. 5.

Under the new pact, the two countries agreed to reduce their deployed nuclear warheads to 1,550 each, or 30 percent below the current level of 2,200, and cut the launchers below 700 each.