Sen. Bernie Sanders Bernie SandersThe Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power Bernie Sanders: 'This is an election between Donald Trump and democracy' The Hill's 12:30 Report: Trump stokes fears over November election outcome MORE (I-Vt.), a 2020 White House hopeful, said on Sunday that he doesn't want talks between President Trump and North Korea leader Kim Jong to be merely a photo opportunity.

"I don't have a problem with him sitting down and negotiating with our adversaries, I don't want it to be a photo opportunity. We need real diplomacy," Sanders said on ABC's "This Week."

Sanders said that while Trump is meeting with the North Korean leader, the president has "weakened the State Department."

The senator also said the U.S. needs a "strong State Department to move forward diplomatically." ADVERTISEMENT

Trump earlier Sunday became the first sitting U.S. president to cross into North Korea. He later announced that stalled nuclear talks between the U.S. and North Korea would resume.

"The whole worlds' media was attracted there. What's going to happen tomorrow and the next day?" Sanders asked.

He also called out Trump for "almost moving toward a war with Iran," and for vetoing legislation passed in the House and Senate to remove U.S. troops from the war in Yemen.

A move to override Trump's veto failed in the Senate in May.