US President Donald Trump is meeting a top North Korean negotiator amid speculation about a possible new summit between the two countries' leaders.
The talks with Kim Yong-chol at the White House are focused on North Korean denuclearisation, spokeswoman Sarah Sanders says.
He is expected to deliver a letter from leader Kim Jong-un to Trump.
Little progress has been made on denuclearisation since their historic summit in Singapore last June.
Speculation is mounting that a second meeting could be held in Vietnam.
Kim Yong-chol's visit to Washington is the first sign of movement in nuclear diplomacy with North Korea for months, BBC state department correspondent Barbara Plett Usher reports.
Kim Jong-un's letter is expected to lay the groundwork for another summit, our correspondent adds.
Who is Kim Yong-chol?
Gen Kim, a former spymaster often referred to as Kim Jong-un's right-hand man, has emerged as North Korea's lead negotiator in recent talks with the US.
He is a controversial figure, accused of masterminding attacks on South Korean warships during his time as military intelligence chief in 2010.
Arriving in Washington on Thursday, he met Secretary of State Mike Pompeo. The state department called it "a good discussion".
In a visit in June, he delivered a letter to Trump ahead of historic talks between both countries.
What could these talks achieve?
It is not clear. The last time Kim went to the US, his letter to Trump appears to have helped get the Singapore summit back on track.
Negotiations between both countries have stalled since then, but this meeting could be what it takes to restart talks.
Earlier this month, Trump said that the US and North Korea were negotiating over a location for another summit but US officials have not provided any further details.
The meetings in Washington could finalise plans for the summit, but just as important, analysts say, would be an understanding of what the agenda would be.
In a new year's speech a few weeks ago, Kim said he was committed to denuclearisation, but warned that he would change course if US sanctions remained.
Both parties signed a pledge in Singapore to denuclearise the Korean peninsula, though it was never clear what this would entail.