(CNN) The United States is getting closer to reaching a "safe third country" agreemen t with Guatemala, according to multiple US sources familiar with the negotiations.

Such an agreement would require migrants who pass through Guatemala to apply for asylum there, rather than continuing to the US. This would likely have the effect of preventing some migrants from applying for asylum in the US.

"Every week it's closer," said an administration official.

The US and Guatemala have been working daily to reach a safe-third agreement, said the official, who added that there "has been a lot of progress" but also some setbacks in the negotiations.

Acting Homeland Security Secretary Kevin McAleenan has advocated this type of agreement. In June, President Donald Trump tweeted that Guatemala was "getting ready to sign a Safe-Third Agreement."

Officials from both countries are closing in on the agreement amid multiple efforts by the Trump administration to stem the flow of migrants arriving at the US-Mexico border. Under US law, migrants are allowed to claim asylum once on US soil.

There's a caveat, however, for those who come through safe third countries, meaning countries the US has entered into an agreement with. The United Nations' refugee agency defines "safe country," in part, as "being countries in which refugees can enjoy asylum without any danger."

Before reaching an agreement, the US is working to make sure there are sufficient protections in place for people who would claim asylum in Guatemala, according to an administration official. There are almost daily phone calls, translating documents back-and-forth to reach an agreement, according to the official.

"ASAP," said a DHS official about the agreement on Thursday.

The "will is there on both sides" to come to an agreement, added the official, who pointed out that the upcoming runoff election in Guatemala puts additional pressure to get something done in the next few weeks before the administration enters "lame-duck" status.

The push to reach an agreement comes days before Guatemalan President Jimmy Morales will be in Washington. Morales plans to travel to DC on Monday to discuss security, migration and the economy, according to a statement by the country's government on Twitter.

Over recent months, migrants from the Northern Triangle countries of Guatemala, El Salvador and Honduras have accounted for the majority of apprehensions at the southern border. They've had to transit Mexico to reach the border, and upon arriving in the US some have turned themselves in to Border Patrol and claimed asylum.

"If an agreement is reached, it's a big deal in combating illegal immigration and should lower the monthly apprehension numbers" at the US-Mexico border, said another administration official, who also said the deal appeared close.

A State Department spokesperson for Western Hemisphere Affairs declined to comment on the agreement or discussions with Guatemala.