WASHINGTON — The Trump administration was caught between allies at home and abroad and the reality of global economics as it reinstated sanctions Monday on Iran, forced to carve out exemptions for important allies and back off on measures that could have been even more punishing for Tehran.

The U.S. granted waivers to allow China and seven close U.S. partners and allies to continue importing Iranian crude and other petroleum products without penalty, bowing to concerns that a complete end to Iran’s exports would cause a major spike in world oil prices and cause other economic disruptions. Trump conceded that reality on his way to a last-minute campaign event a day before critical midterm congressional elections.

“We have the toughest sanctions ever imposed but on oil we want to go a little bit slower because I don’t want to drive the oil prices in the world,” he told reporters. “I could get the Iran oil down to zero immediately, but it would cause a shock to the market.”

The newly reinstated sanctions target Iran’s energy, financial and shipping sectors and are aimed at forcing Iran to end ballistic missile program and end its support for armed movements throughout the Middle East.

The measures restore all the U.S. sanctions that had been lifted under the 2015 accord that gave Iran billions of dollars in sanctions relief in exchange for curbs on its nuclear program, a deal that Obama administration critics had argued was too soft on the Islamic Republic.