(CNN) - President Donald Trump is not backing away from threats to close the U.S. border with Mexico as soon as this week, and a source says the White House is considering appointing a "border or immigration czar."
The president has focused in recent days on the increase in migrants arriving at the border.
He tweeted over the weekend: “Mexico must use its very strong immigration laws to stop the many thousands of people trying to get into the USA. Our detention areas are maxed out & we will take no more illegals. Next step is to close the Border!”
In comments to reporters he then vowed, “We’ll keep it closed for a long time. I’m not playing games.”
The threats follow the highest month of undocumented migrant crossings in 11 years, according to U.S. Customs and Border Protection.
Still, acting Secretary of Defense Patrick Shanahan said that, as of late Monday morning, the Pentagon had not yet been asked to support closing the border.
"It's a very dynamic and fluid situation,” he said. “I'll be having conversations with the secretary of state today and most likely Secretary (of Homeland Security Kirstjen) Nielsen."
White House officials have insisted it’s really on the table. Kellyanne Conway said it “certainly isn’t a bluff” on Fox News on Sunday. And acting Chief of Staff Mick Mulvaney told ABC News that border officers at ports of entry would have to be redeployed “in the desert where we don’t have any wall.”
“We hate to say we told you so, but we told you so,” he said. “We need border security and we're going to do the best we can with what we have."
Mulvaney defended the president’s decision to discontinue aid to Honduras, Guatemala and El Salvador for not doing more to help stem the flow of migrants. He said they need to "do more about not allowing their people into Mexico.
“They can help us, we need them to do that, if not it makes very little sense for us to continue to send them aid," he said.
Sources familiar with the discussions say top White House officials and Trump are considering creating the immigration czar to help oversee the administration's efforts to contain and manage the surge of migrants.