After months in detention, two Americans who had been held prisoner in North Korea soon will be back in the United States following a rare visit by a top U.S. official to the reclusive nation and a letter from President Barack Obama.

Kenneth Bae and Matthew Todd Miller, the last two American detained in North Korea, were due to arrive at Joint Base Lewis-McChord in Washington state around midnight ET (9 p.m. PT).

The pair were released after Director of National Intelligence James Clapper went to Pyongyang as an envoy of President Barack Obama, a senior State Department official told CNN.

Clapper delivered a letter from Obama, addressed to North Korean leader Kim Jong Un, describing Clapper as "his personal envoy" to bring the Americans home, a senior administration official told CNN on Saturday.

The letter was "short and to the point," the official said. Clapper did not meet with Kim.

Clapper had no guarantee he would bring the Americans home, a senior State Department official told CNN.

The North Korean government issued a statement about the release, saying it received an "earnest apology" from Obama for the men's actions. It also said the two were "sincerely repentant of their crimes and (were) behaving themselves while serving their terms."

According to the statement, the first chairman of North Korea's National Defense Commission ordered the release.

China assisted in the monthslong process of arranging the release, the official said.

Clapper's visit came after North Korea contacted the U.S. government unexpectedly and urged the administration to send a Cabinet-level official to North Korea's capital to discuss the detained Americans, according to two sources close to the matter.

A U.S. official told CNN that Washington believes Pyongyang reached out to show it had the clout to get a Cabinet-level official to come and doing so would help solidify Kim's power. The request came about two weeks ago, the official said.

Clapper ended up canceling an event in New York on Wednesday as the trip was being arranged, an Obama administration official said. He went to Pyongyang "prepared to listen" on other issues, but that his sole focus was to bring Bae and Miller home, according to the same official.

In fact, an official in Clapper's office said the talks didn't even touch on North Korea's controversial nuclear program. And other U.S. officials said there was no "quid pro quo" for the men's release.

Clapper's office said the U.S. government is facilitating the two men's return home. Bae's family is to meet the plane but will not grant media interviews.

Clapper and a U.S. delegation also are on the flight.

Bae's sister, Terri Chung, told CNN that her family spent Saturday morning shedding happy tears and spreading the good news among relatives and friends.

"Words cannot adequately express our relief and gratitude that Kenneth is finally coming home!" the family added later in a full statement. "We have been waiting for and praying for this day for two years. This ordeal has been excruciating for the family, but we are filled with joy right now."

There was no immediate reaction from Miller's family.

Obama expressed appreciation for Clapper's efforts "on what was obviously a challenging mission" and happiness Bae and Miller will soon be home.

"It's a wonderful day for them and their families," the President said.

(CNN)