The White House is declaring the recovery of the American journalist Austin Tice a “top priority” in the wake of Syrian rebels running the autocratic head of state out of the country, according to national security adviser Jake Sullivan.

Sullivan told ABC’s Good Morning America on Monday that the US government was actively seeking information about Tice’s whereabouts, communicating through Turkish intermediaries and with contacts on the ground in Syria about the journalist who has been missing for over 12 years.

“This is a top priority for us – to find Austin Tice, to locate the prison where he may be held, get him out, get him home safely to his family,” Sullivan said.

Tice, a former US marine and freelance journalist from Houston, was abducted in August 2012 while reporting on the uprising against then President Bashar al-Assad in Damascus, whose family’s more than 50-year autocracy was crushed as he fled to Russia.

According to data by the Committee to Protect Journalists, Tice is one of at least five journalists being held in Syria on undisclosed charges, and the only American.

It is unclear, however, if Tice is still alive. And because Hayat Tahrir al-Sham – a former al-Qaida offshoot that overthrew Assad’s regime in a matter of days – is designated by the United States as a terrorist organization, the US cannot hold direct talks with its leadership.

But those same insurgent groups have been documented releasing thousands of prisoners previously held under Assad’s grip, offering a glimmer of hope for Tice and his family.

President Joe Biden expressed cautious optimism, telling reporters on Sunday that the US government believed Tice was alive.

“We think we can get him back, but we have no direct evidence to that yet,” Biden said.

Tice’s parents, Marc and Debra, remain hopeful. “Austin Tice is alive, in Syria, and it’s time for him to come home,” they said in a statement.

The FBI has also renewed a $1m reward for information leading to Tice’s safe return. The US also has a $10m bounty for the HTS militant leader Abu Mohammad al-Jolani.

According to the Syrian Network for Human Rights, Tice would be among 135,000 people detained or disappeared by the Syrian government during the country’s prolonged civil war.