Washington (CNN) Bangkok, Hanoi and Hawaii have been visited by White House scouting teams as they search for a location for a potential second summit between North Korean leader Kim Jong Un and President Donald Trump, according to a source familiar with the planning process.

On Sunday, Trump said that the US is "negotiating a location" for a second summit with Kim and the two had spoken "indirectly."

The US has not decided on a top pick and the list, which could expand, has not yet been presented to the North Koreans. There have not been any meetings between the US and North Korean officials in these locations yet, according to the source.

Working level discussions will be required to pick a date and location but getting both parties to the table has proved to be a challenge. Late last year a planned meeting in New York City between the US and North Korea was canceled and there is no future meeting on the calendar. Stephen Biegun, the US special representative to North Korea, has not met with his counterpart one-on-one since taking the job, though he did travel to Pyongyang with Secretary of State Mike Pompeo in October.

The State Department would not say when the next round of working level talks will happen but claimed that there are still open lines of communication.

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