ISTANBUL -- In August 2012, the battle for Aleppo in Syria was just beginning to heat up, and the fighting on the ground was becoming more and more dangerous not just for the men of the Free Syrian Army but also for journalists in the country covering the conflict. Austin Tice was one of the first journalists to disappear in the country. He was embedded with opposition rebels near the Lebanese border. It has been 1,000 days since Tice first went off the grid -- off of social media and disconnected from friends and family -- and his family is still seeking answers.

Tice's mother spoke to reporters in Beirut on Tuesday and urged the U.S. and Syria  to work together to free him.

"We ask both governments to work together and to work effectively to locate Austin and to secure his safe release," Debra Tice told Reuters in Beirut. "We hear that he is well, that he is safe, which is of course very important, and the most important thing is for us to stay patient."

When the Islamic State group, also known as ISIS, began releasing videos of missing journalists in Syria, the journalism community began to wonder if Tice was also being held hostage by the Sunni militant group. But months passed without any indication that the group was holding Tice. Debra Tice said she still does not know who is holding her son captive but that the U.S. government should be doing more to find him.

"The Syrian government denies holding Austin Tice, but we believe that it has the ability, it can do a lot, so that Austin Tice returns home safe and sound," Reporters Without Borders Secretary-General Christophe Deloire told a news conference, Reuters reports.

Debra Tice said in the briefing to reporters that she has "every reason to believe" her son is still alive. 

It is still unclear who is holding Tice in Syria. When Tice disappeared 1,000 days ago in the country, he was embedded with a battalion in the Free Syrian Army -- an opposition umbrella organization that has since largely collapsed, its groups splintering off to join other, more extremist organizations such as Ahrar al Sham and Jabhat al Nusra, the al Qaeda offshoot in Syria.

Tice was last seen with the Free Syrian Army in a town close to the Lebanese border, while celebrating his birthday.

This was his last tweet:


At the time of his disappearance, Tice, now 33, was traveling with the men of a Free Syrian Army battalion and was without a fixer, or security. The fixer -- a local contact who arranges interviews and logistics -- who originally got him into the country (the same person who worked for this journalist when she was a freelancer in Syria) has since vanished from the Syrian battlefield and social media. He has been unreachable since the winter of 2013. 

Dozens of journalists have gone missing in Syria over the past four years, according to the Committee to Protect Journalists. Some of them have been executed by ISIS, including James Foley, who worked with several U.S. news outlets, including Global Post. Tice was a freelancer as well. A former U.S. marine, he had also attended Georgetown Law School. 

"I long to hold my son in my arms," Debra Tice said Tuesday in the news briefing. "I want my family to be whole again."