The United Nations refugee agency said Tuesday it has "serious concerns" about the Trump administration's controversial plans to send migrants seeking asylum in the U.S. to Guatemala and other Central American countries.

The approach is "at variance with international law that could result in the transfer of highly vulnerable individuals to countries where they may face life-threatening dangers," the United Nations High Commissioner for Refugees said in a statement .

The agency also said it was not a party to any asylum agreements reached between the U.S. and Guatemala, Honduras and El Salvador – notable because the Department of Homeland Security, which oversees U.S. immigration, has indicated that the U.S. would work with the U.N. agency to build up the capabilities of those countries to provide asylum as part of the agreements.

The Trump administration this summer inked a deal with the Guatemalan government that would allow the U.S. to send asylum-seekers to Guatemala to apply for protection there instead. The administration later reached similar agreements with El Salvador and Honduras.

A rule released Monday and officially published in the Federal Register on Tuesday clears the way for those agreements to be implemented, starting with Guatemala. Under the policy, the U.S. can deport asylum-seeking migrants from the U.S. to Guatemala, even if the migrants did not pass through Guatemala on the way to the U.S.

The asylum agreements with the three Central American countries, commonly known as the Northern Triangle, are similar to "safe third country" deals, or diplomatic means used to deny migrants asylum by deeming that the countries the migrants passed through are capable of offering asylum. Before the recent Northern Triangle agreements, the U.S. had such an agreement with just one country: Canada.

The Trump administration struck the deals as part of a broader effort to severely stem the flow of asylum-seekers appearing at the U.S. border and entering into the U.S. asylum system.

Advocates and immigration organizations have blanched at the recent agreements, which they say will put migrants already fleeing harm and persecution at risk of violence.

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Citizens of the Northern Triangle countries have fled the region in large numbers in recent years, driving the number of apprehensions at the southern U.S. border last fiscal year to totals not seen in over a decade.

The region has high levels of violence and poverty. Guatemala is one of the most dangerous countries in the world, according to the State Department, and struggles with "endemic poverty, an abundance of weapons, a legacy of societal violence, and the presence of organized criminal gangs." El Salvador has the highest murder rate in the world, and Honduras and Guatemala have rates that are among the highest, according to the most recent U.N. data. The State Department has issued travel advisories for U.S. citizens to all three countries.

Homeland security officials have touted the work of the U.N. refugee agency when speaking about the agreements, indicating that the U.S. will build up the fledgling asylum capabilities of the countries by assisting and funding the work of the agency.

Homeland security documents recently obtained by Buzzfeed News , however, suggest that cooperation between the entities is not going smoothly.

"It is our understanding that for some time now there has been friction between the [Government of Guatemala] and UNHCR regarding UNHCR's role in the implementation" of the asylum agreement, a brief prepared for newly appointed acting Homeland Security Secretary Chad Wolf said, Buzzfeed reported. Guatemalan officials have said that the U.N. agency would not have access to its asylum program, though the U.N. told the U.S. that it would organize orientation services for asylum-seekers sent to Guatemala.