WASHINGTON, April 13 (Xinhua) -- U.S. President Barack Obama said Tuesday the two-day nuclear security summit made the world more secure, as participating countries came not only to make pledges of future action, but also to take meaningful steps that can be implemented right now.

In a press conference after the summit, Obama said "real progress" has been achieved by the adoption of a communique vowing commitment to secure vulnerable nuclear materials in four years, a goal he outlined in a speech in Prague one year ago, and a work plan outlining specific steps to that effect.

"We made real progress in building a safer world" Obama said.

U.S. President Barack Obama speaks at a news conference after the two-day Nuclear Security Summit closed in Washington D.C., capital of the United States, April 13, 2010.

As to specific ways to achieve that goal, Obama said all participating nations reaffirmed that it is the fundamental responsibility of nations to "maintain effective security of the nuclear materials and facilities under our control."

He said the threat of nuclear terrorism cannot be addressed by countries working in isolation, and existing institutions and mechanisms needed to be strengthened, and that include the United Nations, the International Atomic Energy Agency and others.