Panama President Jose Raul Mulino
AFP

Deportation flights from Panama for undocumented US-bound migrants who have crossed the lawless Darien jungle from South America are expected to start imminently, a US official said Tuesday.

Washington this month pledged $6 million in funding for migrant repatriations from the Central American nation in the hope of reducing irregular crossings at its own southern border.

The program was expected to use "large numbers" of charter and commercial flights to send back migrants who cross the Darien Gap, said Marlen Pineiro, an official at the US Department of Homeland Security.

"We're still negotiating (with Panama), but the focus of this program is deportations and expulsions," she said at a news conference in Panama City.

"I don't want to give a date yet, but I think we're going to start imminently," Pineiro added.

The Darien Gap between Colombia and Panama has become a key corridor for migrants traveling overland from South America through Central America and Mexico to the United States.

Despite the dangers posed by treacherous terrain and violent criminal gangs, more than half a million undocumented migrants -- mostly Venezuelans -- crossed the Darien last year.

Transit countries such as Panama and Mexico have come under increased pressure from Washington to tackle the highly contentious migration issue in a US election year.

Jose Raul Mulino, Panama's new president, vowed during his election campaign to deport migrants and close the key route.

After he was sworn in on July 1, the conservative lawyer said his country would no longer be a "transit" point for undocumented migrants.

However, he appeared to soften his tone last week, saying, "We cannot forcibly repatriate" migrants.