UNITED NATIONS (AP) -- President Barack Obama's administration will seek to end Iran's nuclear ambition and its support for terrorism, the U.S. ambassador to the United Nations said Thursday -- drawing an immediate rebuke from Iran's U.N. envoy. Iran has never and will never try to acquire nuclear weapons, Ambassador Mohammad Khazee said in a letter to the U.N. Security Council immediately after U.S. Ambassador Susan Rice spoke. He dismissed her allegation that Iran engages in terrorism as "baseless and absurd." Iran insists it is enriching uranium to produce nuclear energy for civilian purposes, but the U.S. and many European countries accuse Tehran of secretly seeking to build nuclear weapons. Rice brought up Iran at an open meeting of the Security Council on Iraq, saying the long-term U.S. commitment to Iraq and the reduction of the U.S. military presence there had to be understood "in a larger, regional context" that included Afghanistan, the Middle East and Iran. The United States "will seek an end to Iran's ambition to acquire an illicit nuclear capacity and its support for terrorism," Rice said. She said the U.S. will aim to encourage both Iran and Syria to become "constructive regional actors." Her comments came as the Obama administration is reviewing U.S. policy toward Iran. Obama has signaled a willingness for dialogue with Iran, particularly over its nuclear program. At his inauguration last month, the president said his administration would reach out to rival states, declaring "we will extend a hand if you are willing to unclench your fist." Iranian President Mahmoud Ahmadinejad responded by saying Iran would welcome talks with the United States -- but only if there was mutual respect. Iranian officials have said that means the United States would need to stop making "baseless" accusations against the Islamic Republic. In his letter, Khazee said, "It is unfortunate that, yet again, we are hearing the same tired, unwarranted and groundless allegations that used to be unjustifiably and futilely repeated by the previous U.S. administration." On Wednesday, Iranian state radio said Secretary of State Hillary Clinton's choice of Dennis Ross as her special adviser on the Persian Gulf signaled no change in the U.S. stance toward Iran. "Ross strongly backs stepping up sanctions against Iran ... (and) supports profound U.S.-Israeli cooperation to confront Iran's nuclear activities," the broadcast said. The latest International Atomic Energy Agency report says Iran now possesses 1,010 kilograms -- 2,222 pounds -- of low-enriched uranium, raising concern that it now has sufficient uranium and the means to enrich it further to produce both nuclear fuel and the fissile core of nuclear warheads.