(CNN) The US and North Korea are seriously considering exchanging liaison officers, an incremental step towards building formal diplomatic relations, two sources with knowledge of the discussions told CNN.

News of the discussions comes days ahead of President Donald Trump and North Korean leader Kim Jong Un's second summit, which is set to take place in Vietnam at the end of the month.

Trump and Kim met in Singapore last year, and both leaders there signed a joint statement that included commitments from each country "to establish new US-DPRK relations in accordance with the desire of the peoples of the two countries for peace and prosperity."

This statement left the door open to some kind of re-establishment of formal relations if things were to go well, the sources said, adding that the current stalemate has left North Korea expecting some significant gesture on the part of the US.

The two high-level diplomatic sources said the first step forward could be the exchange of officers. On the US side, sources said there would be several liasion officers sent to set up office in North Korea, led by a senior foreign service officer who speaks Korean, if this plan were to move forward.

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