Obama, who is attending the Group of Eight summit in L'Aquila, said the purpose of the international gathering would be for nations to develop steps that can be taken to "secure vulnerable materials, combat nuclear smuggling, and deter, detect and disrupt attempts at nuclear terrorism," a statement released by the White House said.
The summit also would address the development and expansion of peaceful nuclear energy worldwide.
"We should not wait for an act of nuclear terrorism before working together to collectively improve our nuclear security culture, share our best practices and raise our standards for nuclear security," the statement by the U.S. president said.
The G8 leaders Wednesday endorsed Obama's three-prong strategy to curb international nuclear threats: find ways to reduce and eventually eliminate existing nuclear arsenals; strengthen the non-proliferation treaty to halt the spread of nuclear weapons to more countries; and to prevent terrorists from getting their hands on nuclear weapons or materials.
The G8 leaders said they welcomed Obama's announcement to seek ratification of the Comprehensive Nuclear Test Ban Treaty, and support early start of negotiations on a fissile material cut-off treaty.
The leaders said they were heartened by the nuclear disarmament measures taken by nuclear weapons states, including the announcement by the United States and Russia of their intent to conclude an agreement to replace START before it expires this year.
The G8 leaders urged Iran to comply with the United Nations Security Council resolutions regarding its nuclear program and to cooperate with the International Atomic Energy Agency.
They strongly condemned the nuclear test and ballistic missile launches conducted by North Korea this spring. They urged North Korea to abide by U.N. resolutions and abandon all nuclear weapons and existing nuclear programs and ballistic missile programs "in a complete, verifiable and irreversible manner."