President Trump is weighing a critical decision in the four-day-old war between Israel and Iran: whether to enter the fray by helping Israel destroy the deeply buried nuclear enrichment facility at Fordo, which only American “bunker busters,” dropped by American B-2 bombers, can reach.

If he decides to go ahead, the United States will become a direct participant in a new conflict in the Middle East, taking on Iran in exactly the kind of war Mr. Trump has sworn, in two campaigns, he would avoid. Iranian officials have already warned that U.S. participation in an attack on its facilities will imperil any remaining chance of the nuclear disarmament deal that Mr. Trump insists he is still interested in pursuing.

Mr. Trump has encouraged Vice President JD Vance and his Middle East envoy, Steve Witkoff, to offer to meet the Iranians this week, according to a U.S. official. The offer may be well received.

Mr. Trump, at the Group of 7 summit in Canada, said late on Monday, “I think Iran basically is at the negotiating table, they want to make a deal.”

If such a meeting happened, officials say, the likely Iranian interlocutor would be the country’s foreign minister, Abbas Araghchi, who played a key role in the 2015 nuclear deal with the Obama administration and knows every element of Iran’s sprawling nuclear complex. Mr. Araghchi, who has been Mr. Witkoff’s counterpart in recent negotiations, signaled his openness to a deal on Monday, saying in a statement, “If President Trump is genuine about diplomacy and interested in stopping this war, next steps are consequential.”

“It takes one phone call from Washington to muzzle someone like Netanyahu,” he said, referring to the Israeli prime minister. “That may pave the way for a return to diplomacy.”