U.S. President Donald Trump and South Korea's new president, Lee Jae-myung, agreed to work toward a swift tariff deal in their first phone call since Lee was elected this week, Lee's office said Friday.

Trump has imposed tariffs on South Korea, a long time ally with which it has a bilateral free trade deal, and pressed it to pay more for the 28,500 U.S. troops stationed there.

Separately, Trump allies have aired concerns about Lee's more conciliatory stance toward China, Washington's main geopolitical rival.