Jerusalem's top official at the nuclear security conference said Tuesday that the first session of the conference had not produced any criticism of Israel's alleged nuclear weapons program.

Dan Meridor, the deputy prime minister who is heading Israel's delegation to the nuclear security summit, summed up the first day of deliberations Tuesday in Washington by declaring that "thus far, there has been no ambush."

"We are operating in an atmosphere of cooperation both inside the conference and on the sidelines of it," said Meridor, who also holds the title of intelligence and atomic energy minister. "This is a respectable forum of countries that are concerned [with the issue of nuclear proliferation] and our participation here is testament to our position in the world."

"We are part of the world that is dealing with this threat," Meridor said. "We are not the main topic on the agenda here, nor were we mentioned by any of the speakers, including speakers who one may think would have mentioned us. Iran was mentioned here and there despite the fact that the main issue is the effort to prevent the spread of nuclear weapons and to deny terrorist organizations that are liable to one day possess nuclear capability."

In his talks with leaders of Arab states, including Jordan's King Abdullah and the Egyptian foreign minister, Meridor said he has yet to hear criticism of Israel's nuclear policy. The deputy premier said he has yet to speak with Turkish Prime Minister Recep Tayyip Erdogan, who has pledged to raise the issue during the summit.

"Overall, the message is clear, and the statements are being made in a respectful, organized manner," Meridor said. "I have yet to run into any 'ambush' either in my talks with world leaders as well as those from Arab countries."

Meridor added that the issue of a possible Israeli strike against Iran, which the presidents of France and Russia said would be a "disaster," has also not been broached during conversations in Washington.

Meridor refused to say whether Prime Minister Benjamin Netanyahu erred in withdrawing from the summit. When asked if countries have refrained from criticizing Israel due to Netanyahu's absence, Meridor said: "Maybe there is a connection there."

Netanyahu announced last week that he would not attend the conference for fear that certain countries would use the event as a platform to denounce Israel's nuclear policy.

When asked what steps Israel is willing to take to help the international effort to slow the spread of nuclear weapons, Meridor said: "In recent years we have done quite a bit in helping guard nuclear installations. We have done much work in this regard, and that is no secret."

Obama: Risk of terrorist nuclear attack rising

Obama warned earlier Tuesday that the threat of terrorists using an atomic weapon in a catastrophic attack has risen, and called on all countries to formulate a plan to keep nuclear material safe.

Obama opened a full day of talks at an unprecedented summit in Washington to address that challenge. Leaders and top officials from more than 47 nations are attending the summit, the largest hosted by an American president since 1945.

"Terrorist networks such as al-Qaida have tried to acquire the material for a nuclear weapon. And if they ever succeeded, they would surely use it," Obama said.

"Were they to do so, it would be a catastrophe for the world, causing extraordinary loss of life and striking a major blow to global peace and stability," he added.

Obama called on countries to adopt a "concrete" plan to secure nuclear materials within four years as part of his broader agenda for a nuclear-free world outlined in a Prague speech a year ago.

"Two decades after the end of the Cold War, we face a cruel irony of history," Obama said. "The risk of a nuclear confrontation between nations has gone down, but the risk of nuclear attack has gone up."

Obama announced plans to hold a follow-up summit hosted by South Korea in 2012.

The goals of the ongoing talks include strengthening international safeguards to account for and adequately secure stockpiles of nuclear material and reduce the use of highly enriched uranium used in civilian reactors. The substance is a key ingredient for a weapon.

"We have the opportunity as individual nations to take specific and concrete actions to secure the nuclear materials in our countries and to prevent illicit trafficking and smuggling," he said.

Ukraine and Canada announced during the summit plans to give up highly enriched uranium as part of a broader, long standing effort led by the United States and Russia to take back the dangerous fuel and convert civilian reactors into using the much safer low enriched uranium.

Obama wants to strengthen efforts to halt the spread of nucleartechnology on the black market and more stringent prosecution of individuals responsible for the illicit trade.

The summit comes after a U.S.-Russian pact to reduce their existing nuclear arsenals by one-third, a treaty Obama signed Thursday with Russian President Dmitry Medvedev. It also comes after Obama announced a shift in nuclear policy that pledged to not use nuclear weapons against countries which do not have them. That policy, however, excluded Iran and North Korea because they are not seen as cooperating on non-proliferation.

While the focus of the summit is on securing nuclear stockpiles, Iran's continued defiance of international demands to halt uranium enrichment and come clean about its nuclear activities has been a sub-text at the gathering. Iran denies Western allegations that its nuclear program is designed to achieve a weapons capability.

The topic was high on the agenda when Obama met with Chinese President Hu Jintao on Monday as part of an effort to persuade a reluctant Beijing to support tougher UN Security Council sanctions. A senior White House official told reporters after the meeting that China signaled a willingness to cooperate in drafting sanctions.

Obama also met with the leaders of India, Pakistan, South Africa, Jordan, Malaysia and a number of other countries before convening the formal session.

Meanwhile, U.S. Secretary of State Hillary Rodham Clinton and Russian Foreign Minister Sergei Lavrov are expected to sign a deal Tuesday to implement an agreement for the two countries to each dispose 34,000 metric tons of weapons-grade plutonium from existing stockpiles.

The Plutonium Management and Disposition Agreement has been in the works for more than a decade and was agreed to in principle in 2000, but Moscow and Washington had differed over protocols to implement the pact.