WASHINGTON — The Obama administration announced an agreement on Tuesday with other major powers, including Russia and China, to impose a fourth set of sanctions on Iran over its nuclear program, setting the stage for an intense tug of war with Tehran as it tries to avoid passage of the penalties by the full United Nations Security Council.

The announcement came just a day after Iranian leaders announced their own tentative deal, with Turkey and Brazil, to turn over about half of Iran’s stockpile of nuclear fuel for a year, part of a frantic effort to blunt the American-led campaign for harsher sanctions.

“This announcement is as convincing an answer to the efforts undertaken in Tehran over the last few days as any we could provide,” Secretary of State Hillary Rodham Clinton told the Senate Foreign Relations Committee, describing the agreement as a “strong draft.”

But even if the Security Council adopts the new sanctions, it is unclear whether the provisions — including a mandate to inspect Iranian ships suspected of entering international ports with nuclear-related technology or weapons — would inflict enough pain to force Iran to halt its uranium enrichment and cooperate with international inspectors. None of the previous three sets of sanctions passed by the Council during the Bush administration succeeded in their goal: forcing Iran to end its enrichment of uranium and to answer the many questions posed by international inspectors related to their suspicions about Iranian research into nuclear weapons.