Fears of Wider Mideast Conflict Deepen, With U.S. Seen as ‘Not in Control’

For months, diplomats and analysts in foreign capitals have worried that prolonged political upheaval in the United States could invite aggression abroad, whether in Russia’s waging of war in Ukraine, North Korea’s rogue nuclear ambitions or China’s expansionist designs in the South China Sea.

Now, less than 100 days before Americans elect a new president, that broader geopolitical crisis has erupted in the familiar theater of the Middle East. The targeted killings of Hezbollah and Hamas leaders in Beirut and Tehran have deepened fears of a regionwide conflict — one that the United States, caught up in its own political drama at home, may have little capacity to avert or even contain.

On Wednesday, Secretary of State Antony J. Blinken said the United States had not been involved in, or even informed of, the operation in Tehran, which the Iranian government swiftly blamed on Israel. To some, Mr. Blinken’s statement confirmed a dangerous power vacuum in the region.

“We thought it would be Vladimir Putin or Xi Jinping or Kim Jong-un who would take advantage of this period in the U.S.,” said Vali R. Nasr, a professor of international affairs at the Johns Hopkins School of Advanced International Studies. “Nobody counted on an American ally doing it.”

“This is going to make the region extremely nervous,” said Mr. Nasr, who served in the State Department during the Obama administration. “It’s never good for the United States to be seen as not in control.”