UNITED NATIONS — Arab countries sought to turn attention Tuesday to Israel as delegates from 189 countries debated how to stem the spread of nuclear weapons.On the second day of the monthlong meeting at the United Nations, Arab countries were reiterating calls for a nuclear-free Middle East with criticism of Israel's unacknowledged nuclear arsenal and failure to sign the Nuclear Nonproliferation Treaty (NPT).The first day of the conference was dominated by rhetorical crossfire between the United States and Iran, as Washington pushed for the UN Security Council to approve new sanctions against Iran.On Tuesday, Jordanian Foreign Minister Nasser Judeh expressed frustration at the lack of progress on implementing a nuclear-free Middle East, a goal that was declared in a resolution of a previous meeting of NPT signatoriesHe said that Israel's failure to sign the NPT and allow international monitoring of its nuclear program "renders the NPT a source of instability in the Middle East."Egypt has proposed that this 2010 NPT conference back a plan calling for the start of negotiations next year on such a Mideast zone. The proposal may become a major debating point in the monthlong session.The United States has cautiously supported the idea while saying that implementing the idea must wait for progress in the Middle East peace process. The position reflected a middle ground as the Obama administration sought to satisfy Arab countries while keeping the spotlight of the conference on Iran's nuclear program.Meanwhile, Ahmadinejad continued his campaign to stall the US push for new sanctions. He scheduled a news conference Tuesday afternoon. On Monday, addressing the conference, he rejected the US allegations about Iran's nuclear program, saying Washington has offered not "a single credible proof" that Iran was seeking nuclear weapons. Iran says it only wants the technology for producing nuclear power.The debate about Iran dominated the first day of the month-long conference on how to improve the NPT. The treaty is formally reviewed every five years at a meeting of treaty members — all the world's nations except India, Pakistan, Israel and North Korea, all of which either have confirmed or are believed to have nuclear weapons.The review conference is meant to produce a final document pointing toward ways to better achieve the NPT's goals of checking the spread of nuclear weapons, while working toward reducing and eventually eliminating them.Because it requires a consensus of all parties, including Iran, any final document would be highly unlikely to censure the Tehran government, which would block consensus.US officials have said they will be looking to isolate Iran at the conference and to produce an unofficial document calling for stricter enforcement of the NPT that could be signed by the overwhelming majority of signatory countries.As delegates assess the state of the NPT in UN conference halls, American and European diplomats will be working elsewhere to reach agreement with the sometimes reluctant China and Russia on a fourth round of UN Security Council economic sanctions against Iran.