The Washington Post reports: The near-collapse of nuclear talks with Iran has ushered in what experts on Wednesday described as a dangerous new phase in the decade-long standoff over Tehran’s nuclear program.

A new round of sanctions is scheduled to take effect July 1, increasing the pressure on Iran’s faltering economy. At the same time, prominent Israeli and U.S. politicians are renewing calls for preparations for a military strike to halt Iran’s nuclear progress.

Iranian officials sounded fresh notes of defiance a day after talks concluded in Moscow, blaming Western countries for the lack of progress and insisting that no amount of pressure would persuade Iran to give up its right to a civilian nuclear energy program. The negotiations between Iran and the bloc of countries known as the P5-plus-1 ended late Tuesday with no agreement and no further substantive talks scheduled, other than technical consultations.

“There is not a one of us who is not aware how serious this is,” said a senior Obama administration official, reflecting on the failure to achieve any meaningful agreement with Tehran after three rounds of direct negotiations with Iranian officials since April.

While insisting that diplomatic efforts would continue, the official said the White House was “sober” in assessing the outcome of the Moscow talks, in which Iran was said to have balked at demands for freezing production of a type of enriched uranium that can be easily converted to fuel for nuclear weapons. The United States and its allies contend that Iran is using civilian facilities as a cover for developing a nuclear weapons capability, an assertion Iran denies.

The counterproposals from the Iranian side were “far from where the rest of us are,” leading to the decision to hold low-level technical consultations next month in Turkey so the sides can clarify their positions, said the official, who insisted on anonymity in describing the diplomatically sensitive negotiations.

The United States and other members of the six-nation bloc (the U.N. Security Council’s five permanent members and Germany) pushed hard in the final hours of the Moscow meeting to preserve at least an appearance of continuing negotiations, fearing that a complete failure would increase the likelihood of a military strike. But U.S. officials said they would not agree to open-ended talks that allow Iran to continue adding to its uranium stockpile. “This is not indefinite,” the administration official said.

Iran had sought relief from potentially crippling sanctions as a condition for any concessions on curbs to its nuclear program.

With diplomacy in tatters, Tehran faces the full brunt of a European Union oil embargo on July 1 and new U.S. sanctions targeting the country’s central bank.