The United States is trying to repatriate some 13,500 Americans stranded overseas by the coronavirus pandemic but does not believe it can reach all of them, the State Department said Monday.

With much of the world imposing temporary entry restrictions and airlines slashing flights, the State Department has encouraged Americans to find their own way home while they still can.

Some 13,500 US citizens have reached out to US embassies and consulates around the world "saying they're interested in our assistance," a senior State Department official said.

Some 5,700 people have already been brought back -- including more than 800 out of the Chinese virus epicenter of Wuhan and 1,200 last week from Morocco as well as 300 from the Diamond Princess cruise in Japan, the official said.

"We will bring home thousands more in the coming days and weeks," he said.

But he added: "We're hearing about people who are in very remote locations in very remote parts of the world. It's complicated

"So I'm hesitant to give a guarantee we can bring every single person."

The vast majority of repatriated Americans have come back on planes chartered by the State Department, but more options are under consideration, including Defense Department aircraft, he said.

The State Department said Monday that it was working to arrange transportation for Americans, at their own expense, to fly out of the Democratic Republic of Congo and Burkina Faso as commercial service is being suspended.

But it has otherwise encouraged Americans to look at available commercial options.

Senator Robert Menendez, the top Democrat on the Senate Foreign Relations Committee, has urged President Donald Trump's administration to go further by activating a reserve program that enlists commercial airliners on behalf of the Defense Department.

The Civil Reserve Air Fleet has only been activated twice -- to fly troops for the 1990-91 Gulf War and again in 2003 for the Iraq invasion.