Kim and his entourage visited the presidential palace of Istana hours after he arrived in Singapore on a Air China flight for his summit with Trump on Tuesday.
Menendez spoke Sunday on ABC's "This Week" as President Donald Trump arrived in Singapore ahead of Tuesday's talks with Kim.
It's Kim's pursuit of nuclear weapons that gives his meeting with Trump such high stakes. News that U.S. Secretary of State Mike Pompeo visited North Korea was front page news with a big photo of him shaking Kim's hand the following day in the ruling party newspaper, the Rodong Sinmun.
The understated photo op belied the intensive behind-the-scenes negotiations that continued between the US and North Korean delegations less than 24 hours before Trump was scheduled to meet Kim at the Capella Hotel on the resort island of Sentosa, just off Singapore's southern coast.
The top Democrat on the Senate Foreign Relations Committee says the North Korean leader has already achieved some success just by bringing the American president to the table.
Trump has sought to lower expectations for the summit in recent days, suggesting that it would be the start of a lengthy process to get Pyongyang to begin dismantling its nuclear and ballistic missile programs.
Aware that the eyes of the world were on a moment many people never expected to see, Kim said many of those watching would think it was a scene from a "science fiction movie".
Onlookers clamored to catch a glimpse or a snap cellphone picture of Kim in his black Mercedes limousine as his 20-vehicle motorcade sped from Changi Airport to a protected area at the luxury St. Regis Singapore hotel where he is staying.
One dispatch by the Korean Central News Agency said North Korea and the U.S. would exchange "wide-ranging and profound views" on establishing new relations, building a "permanent and durable peace-keeping mechanism", achieving denuclearization and "other issues of mutual concern, as required by the changed era".
He also told Lee the decision to hold the summit in the island city-state of Singapore was "made very consciously" and offers thanks.
Olivia Enos, policy analyst with the Asian Studies Center at The Heritage Foundation in Washington, said "a successful summit would move beyond mere statements about denuclearization". The session will be expanded to a bilateral meeting and will include advisors.
It was reported that Kim planned to fly back to North Korea in the early afternoon on Thursday, leaving very little time for actual negotiations, although there is still considerable uncertainty about what a deal between the leaders would look like.