President Donald Trump and North Korean leader Kim Jong Un shared a historic handshake Tuesday as they kicked off a meeting that has been months in the making.

READ MORE: The latest from Singapore

The White House said on Monday ahead of the scheduled talks that the meeting between the two leaders, which will focus largely on North Korea’s possible denuclearization, has moved “more quickly than expected.” As a result, Mr. Trump will plan to return to Washington, D.C., about 15 hours sooner than the scheduled end of the summit, which had been set for Wednesday afternoon.

After their greeting, the leaders were scheduled to have a one-on-one meeting, which could last up to two hours. Translators will be joining them.

Here’s guidance from the White House on what to expect for Tuesday’s summit on Sentosa Island, Singapore:

9 p.m. ET Trump expected to participate in a greeting with North Korean leader Kim Jong Un.

Trump expected to participate in a greeting with North Korean leader Kim Jong Un. 9:15 p.m. ET Trump to participate in a one-on-one bilateral meeting with Kim.

Trump to participate in a one-on-one bilateral meeting with Kim. 10 p.m. ET Trump to participate in an expanded bilateral meeting with Kim.

Trump to participate in an expanded bilateral meeting with Kim. 11:30 p.m. ET Trump to participate in a working lunch with Kim.

Trump to participate in a working lunch with Kim. 4 a.m. ET Trump expected to address media.

Trump is expected to take questions from the media at the close of the summit at 4 p.m. local time Tuesday (4 a.m. ET Tuesday in the U.S.). Watch here.

As the PBS NewsHour’s Nick Schifrin noted over the weekend, “the only certainty about this summit is the uncertainty.”

READ MORE: What could really happen at the Trump-Kim summit?