WASHINGTON (AP) — Secretary of State John Kerry warned Congress Wednesday against scuttling a historic opportunity for a nuclear pact with Iran by pressing ahead with new sanctions while international negotiators seek to prevent Tehran from being able to assemble an atomic weapons arsenal.

Kerry, who as a senator joined the effort to impose crippling oil, trade and investment restrictions on Iran, said the United States and other world powers are united behind an offer they presented to Iranian negotiators in Geneva last week. But he said new action now from U.S. lawmakers could shatter an international coalition made up of countries with interests as divergent as France, Russia and China, endangering hopes for a peaceful end to the decade-long nuclear standoff with the Islamic republic.