​WASHINGTON — The Trump ​a​dministration unveiled new asylum rules Monday that would drastically limit the eligibility of Central American migrants to seek relief at the US-Mexico border.

In a major migrant crackdown, asylum seekers making the dangerous journey to the US would first have to apply for safety in another country on their route, such as Mexico.

If migrants don’t apply for protection from a third country, they would not be eligible for asylum when they attempt to cross into the US, under a new measure announced by the Department of Justice and Department of Homeland Security.

The clampdown is set to take effect Tuesday and it’s the latest attempt by the Trump ​administration to stem the huge flow of migrants seeking relief in the United States.

The rush at the border has led to overcrowded, harmful and unsanitary conditions at strained detention facilities, according to ​news reports.

​Acting ​Department of Homeland Security Secretary Kevin K. McAleenan said until Congress acts to change asylum rules permanently, the interim measure should reduce the “pull” factor for migrants to make the dangerous journey to the US.

“Ultimately, today’s action will reduce the overwhelming burdens on our domestic system caused by asylum-seekers failing to seek urgent protection in the first available country, economic migrants lacking a legitimate fear of persecution, and the transnational criminal organizations, traffickers, and smugglers exploiting our system for profits,” McAleenan said in a statement.

The rule, which will likely face legal challenges, would dramatically decrease the number of people from migrant caravans eligible for asylum when they reach the US.

It would force those fleeing from dangerous conditions to first seek refuge in the first available country they enter after leaving their home.

Only a small minority of the current asylum-seekers are ultimately granted the legal protection in the US.

But many migrants currently stay in the US until their case is adjudicated.

During the budget year for 2009, there were 35,811 asylum claims, and 8,384 were granted.

During the 2018 budget year, there were 162,060 claims filed, and 13,168 were granted.

“The United States is a generous country but is being completely overwhelmed by the burdens associated with apprehending and processing hundreds of thousands of aliens along the southern border,” said Attorney General William Barr in a statement.

The asylum rule would have three exceptions for migrants who were denied asylum in a third country, for migrants who are victims of severe human trafficking and migrants who didn’t travel through a country that signed onto a treaty for refugee protections.

With Post wires