Washington — President Trump defended his handling of conflicts around the world in a speech before the United Nations General Assembly on Tuesday, saying he could "annihilate" Iran while predicting that its leaders would make a deal to end the war after the U.S. midterm elections.

He framed his approach to foreign policy over his first two years back in office as deploying American power to solve "decades of intractable challenges" that previous U.S. leaders have failed to address.

"I do not believe in letting problems fester. They only b...