UNITED NATIONS — The United Nations Security Council on Monday unanimously approved a resolution that creates the basis for international economic sanctions against Iran to be lifted and potentially sets up an angry showdown in Congress.

The 15-0 vote for approval of the resolution, 14 pages long, was written in Vienna by diplomats who negotiated a landmark pact last week that limits Iran’s nuclear capabilities in exchange for ending the sanctions.

Iran has pledged to let in international monitors to inspect its facilities for the next 10 years and other measures that were devised to guarantee that its nuclear energy activities are purely peaceful.

The Security Council resolution, which is legally binding, lays out the steps required for the lifting of United Nations sanctions, not the sanctions imposed separately by the United States and the European Union.

But diplomats have warned that if the United States Congress refuses to lift American penalties against Iran, the Iranians may renege on their commitments as well, which could result in a collapse of the entire deal.

The resolution takes effect in 90 days, a time frame negotiated in Vienna to allow Congress, where members have expressed strong distrust of the agreement, to review it. President Obama, who has staked much of his foreign policy ambitions on the Iran pact, has vowed to veto a congressional rejection of the nuclear accord.

The resolution will not completely lift all Council restrictions on Iran. It maintains an arms embargo, and sets up a panel to review the import of sensitive technology on a case-by-case basis.

It also sets up a way to renew sanctions if Iran does not abide by its commitments. In the event of an unresolved dispute over Iran’s enrichment activities, the United Nations sanctions snap back automatically after 30 days. To avoid the sanctions renewal requires a vote of the Council — giving skeptics, namely the United States, an opportunity to veto it.

Mr. Obama’s critics in Congress, including at least two senior Democrats, objected to the Council vote’s taking place before Congress has had a chance to debate it.

They assert that it would signal an intention to dismantle sanctions, contingent on Iran’s abiding by its commitments, before American lawmakers have had time to vote on it.

The United States ambassador, Samantha Power, speaking immediately after the vote, told the Council that sanctions relief would start only when Iran “verifiably” meets its obligations under the deal.

“We have a responsibility to test diplomacy,” she said.

In an effort to assuage critics, including Israel, Ms. Power went on to say that the United States would continue to scrutinize the “instability that Iran fuels beyond its nuclear program.”

She also called on Iran “to immediately release all unjustly detained Americans,” a reference to three Americans of Iranian descent who have been incarcerated in Iran, including one for nearly four years.

The ambassadors from France and Russia both described the resolution as historic, but used their Council pulpit to emphasize their own positions. The French ambassador, François Delattre, said the pact must be carefully monitored. “We will judge by its actions Iran’s willingness to make this agreement a success,” he said.

The Russian envoy, Vitaly I. Churkin, indirectly nudged the United States to do its part. “We expect all countries will quickly adopt to the new conditions,” he said.

This article was written by Somini Sengupta for The New York Times on July 20, 2015. Somini Sengupta covers the United Nations. She was previously The Times’ bureau chief in Dakar and New Delhi and most recently wrote about technology and the law. She was born in Calcutta, grew up in Canada and California and graduated from the University of California, Berkeley. She is the recipient of the 2004 George Polk Award for foreign reporting.