(CNN)Some time in May 2014, Paul Overby, an American writer in his 70's, disappeared as he was traveling between Khost in Afghanistan and North Waziristan in Pakistan -- a region rife with the Taliban and terror groups such as al Qaeda.
Family reveals American vanished in Afghanistan two years ago
He has not been heard from since.
On Wednesday, his wife went public for the first time with his disappearance, providing a statement to CNN and other media outlets.
Overby's wife, who asked not to be identified by name, last heard from her husband on May 16, 2014, as he was preparing to cross the border into Pakistan. Until then, they had spoken every day on the phone.
Overby, who frequently traveled to Afghanistan and Pakistan and was writing a book about the current war in Afghanistan, was on his way to interview Siraj Haqqani, the leader of the Haqqani network, which is a component of the Taliban and is responsible for many of most lethal bombing attacks in the Afghan capital, Kabul.
In 2015, Haqqani was appointed deputy leader of the Taliban. The US State Department is offering a $10 million reward for information about him.
Prior to his disappearance, Overby had spent one month in Kabul and a month in Khost, an Afghan province close to the Pakistani border where the Haqqani network has a strong presence.
For the past two and half years, Overby's family had kept his disappearance a secret and had requested media outlets that were aware that he was missing, including CNN, also keep the matter confidential out of fear for his life if it became public.
Overby' s disappearance was first reported on Wednesday by Rahimullah Yusufzai, a leading Pakistani journalist, and was confirmed to CNN by Overby's family.
Yusufzai, who has reported authoritatively on the Taliban for more than two decades, wrote that his sources "in the Afghan Taliban group and their faction, Haqqani network" maintain that they don't hold Overby.
In 1993, Overby published "Holy Blood: An Inside Account of the Afghan War," a chronicle of the Afghan resistance to the Soviet occupation during the 1980s. According to Holy Blood, Overby first traveled to Afghanistan in 1988 to chronicle the mujahideen, or "holy warriors," and their fight against the Soviets. He even learned how to shoot an AK-47 assault rifle and fought alongside the mujahideen.
Overby also learned to speak Pashto, the major language of the Afghan-Pakistan border area. When he disappeared, Overby, who is from western Massachusetts, was on his eighth trip to the region.
His family provided emails to CNN that Overby had written in the days before he vanished. They contain discussions about why the US should not retain military bases in Afghanistan -- and fears for his safety.
"We (the US) should not attempt to keep troops in Afghanistan, nor retain any bases ... bases only confirm the deep suspicion of many Afghans that America is planning to use this country as a base from which to contest the mastery of Central Asia, or at least play games, with Iran, Russia, and China," he wrote in one of the emails.
Overby also worried about the potential risk: "As the time slowly spools out I'm not sure how I feel. Safe or in danger?"
The working assumption of the US government and Overby's family is that he is being held captive by the Haqqanis.
At a Pentagon briefing last month, Gen. John "Mick" Nicholson, the overall commander of US forces in Afghanistan, said that the Haqqanis are holding five Americans, although he did not provide the names. US officials said those Americans are: Caitlan Coleman, 31 (Coleman's two toddler sons, who both are under the age of four, were born in captivity); Kevin King, a teacher at the American University of Afghanistan in Kabul who was abducted in August near the university; and Overby.
The Haqqanis also are holding hostage Coleman's Canadian husband, Joshua Boyle, 33, and another American University of Afghanistan teacher, Timothy Weeks, an Australian citizen.
Caitlan Coleman addressed President-elect Donald Trump directly in a video released last month, urging him to secure the release of her and her family. She said the Haqqanis "are not going to simply release our family easily because it is correct. They want money, power and friends. ... We are told there are Afghans who are prisoners in Kabul that these men care about."
Coleman was referring to Anas Haqqani, the brother of Siraj Haqqani, who is in on death row in Afghanistan after a court convicted him in August of raising money to fund terrorism. The Haqqanis have threatened to kill their American hostages if the Afghan government carries out the death sentence on Anas Haqqani.
The incoming Trump administration has a great deal of leverage with the Afghan government, which is strongly hoping for a continued robust US presence in the country that will extend past the end of the Obama administration.
Trump prides himself on the art of the deal, so he could use the leverage he has to secure the release of the American and other Western hostages that are held by the Haqqanis in exchange for the release of Anas Haqqani.
At the same time, Trump could also pressure the Pakistani government, which has long had ties to the Haqqani Network, to secure the release of the American, Canadian and Australian hostages that the terrorist group is holding.
Overby, who has had significant health problems in the past according to his wife, turned 74 on November 27.