A group of top Senate Democrats on Sunday wrote to President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE to urge him that his upcoming summit with North Korean leader Kim Jong Un should produce tangible progress toward the denuclearization of the Korean Peninsula.

The senators wrote that they hope Trump "will execute a serious diplomatic plan" that includes a process to verifiably freeze and dismantle North Korea's nuclear arsenal in conjunction with sanctions and opportunity for further dialogue among allies.

"We believe your next meeting with Kim thus must demonstrate tangible, verifiable progress on denuclearization and reducing tensions with the North," the senators wrote.

ADVERTISEMENT

"As strong advocates for a diplomatic pathway to resolve the North Korea threat, we still believe there is a path forward for tough and principled diplomacy to secure, monitor, and verify the denuclearization of North Korea," they added.

The lawmakers acknowledged Kim's "change in behavior" since the two leaders first met last June in Singapore, an apparent reference to North Korea's halt in missile tests, but noted that the intelligence community has pushed back against Trump's claim that the country no longer poses a nuclear threat.

The letter was signed by eight Democrats, including Senate Minority Leader Charles Schumer Chuck SchumerSenate Democrats introduce legislation to probe politicization of pandemic response Schumer interrupted during live briefing by heckler: 'Stop lying to the people' Jacobin editor: Primarying Schumer would force him to fight Trump's SCOTUS nominee MORE (D-N.Y.) and Senate Foreign Relations Committee ranking member Bob Menendez Robert (Bob) MenendezKasie Hunt to host lead-in show for MSNBC's 'Morning Joe' Senators ask for removal of tariffs on EU food, wine, spirits: report VOA visa decision could hobble Venezuela coverage MORE (D-N.J.).

The president will depart on Monday for Hanoi, Vietnam, where he and Kim will meet on Wednesday and Thursday.

Trump has expressed optimism about the meeting, touting his relationship with Kim and emphasizing that he believes North Korea could emerge as an economic power if it agrees to denuclearize.

The president on Sunday took a swipe at his critics who have expressed skepticism over his ability to secure a deal.

"So funny to watch people who have failed for years, they got NOTHING, telling me how to negotiate with North Korea," Trump tweeted. "But thanks anyway!"