The U.N. nuclear agency chief said Monday that Iran has recently tripled its uranium enrichment and not allowed inspectors to thoroughly investigate its nuclear energy program.

The agency continues to have serious concerns regarding possible military dimensions to Iran's nuclear program, said International Atomic Energy Agency director Yukiya Amano in a March 5 statement.

Amano reported that the IAEA has been able to verify that none of Iran's declared nuclear material is being diverted from its energy program, but could not confirm the absence of undeclared nuclear material.

As Iran is not providing the necessary cooperation...the agency is unable to provide credible assurance about the absence of undeclared nuclear material and activities in Iran, and therefore to conclude that all nuclear material in Iran is in peaceful activities, Amano said.

U.S. and Israel's Approach to Iran

The IAEA's report came as President Barack Obama met with Israeli Prime Minister Benjamin Netanyahu in Washington, D.C., to discuss an agenda dominated by Iran and the potentiality of a preemptive airstrike by Israel against its nuclear energy infrastructure.

On Sunday March 4, the President addressed the American Israel Public Affairs Committee, a non-profit self-described as America's Pro-Israel Lobby, reiterating American support for Israel and commitment to preventing Iran from obtaining nuclear weapons, including the use of military action.

I've said that when it comes to preventing Iran from obtaining a nuclear weapon, I will take no options off the table, and I mean what I say, Mr. Obama said. That includes all elements of American power: A political effort aimed at isolating Iran; a diplomatic effort to sustain our coalition and ensure that the Iranian program is monitored; an economic effort that imposes crippling sanctions; and, yes, a military effort to be prepared for any contingency.

The President, however, expressed his preference for diplomacy over military action earlier in his statements.

I have a deeply held preference for peace over war, Mr. Obama said. I have sent men and women into harm's way. I've seen the consequences of those decisions in the eyes of those I meet who've come back gravely wounded, and the absence of those who don't make it home.

Long after I leave this office, I will remember those moments as the most searing of my presidency. And for this reason, as part of my solemn obligation to the American people, I will only use force when the time and circumstances demand it.

The President added that taking an overly aggressive approach toward Iran does not serve American interests, Israel's or the world as a whole.

Already, there is too much loose talk of war, Mr. Obama said. Over the last few weeks, such talk has only benefited the Iranian government, by driving up the price of oil, which they depend on to fund their nuclear program.  For the sake of Israel's security, America's security, and the peace and security of the world, now is not the time for bluster.

Netanyahu briefly responded to the President's statements by expressing his approval for Obama's support for Israel and its right to defend itself.

More than everything, I value his statement that Israel must be able to protect itself from all threats, said Netanyahu, the Associated Press reported.

The prime minister is expected to put pressure on Mr. Obama to outline the specific circumstances under which the U.S. would take military action against Iran.

Israel officials are also demanding that Iran halt all uranium enrichment before resuming negotiations over sanctions and potential military action, which the White House has rejected as a pre-condition, reported Democracy Now!.

Netanyahu will address AIPAC later Monday evening.