WASHINGTON — President Donald Trump made a new threat Wednesday to send armed soldiers to the U.S.-Mexico border.

Trump tweeted that “Mexico’s Soldiers recently pulled guns on our National Guard Soldiers, probably as a diversionary tactic for drug smugglers on the Border,” but he didn’t offer any support for the drug-smuggling claim.

He tweeted: "Better not happen again! We are now sending ARMED SOLDIERS to the Border. Mexico is not doing nearly enough in apprehending & returning!"

U.S. troops are already at the border to help reduce illegal crossings. The Pentagon has acknowledged more than 5,000 military personnel have been deployed to the southern border, at a cost of $235 million in fiscal 2018 and an estimated $448 million in fiscal 2019.

The Pentagon and U.S. Northern Command did not immediately respond to requests for comment.

The Associated Press quoted White House adviser Kellyanne Conway saying that Trump "is just making clear, as he always has, that he has many different actions at his disposal" to try to stop what the administration calls a humanitarian crisis at the border.

Asked if Trump will, in fact, send additional troops to the border, Conway replied: “He may.”

The tweet came after two U.S. soldiers in a remote area of Texas on April 13 were confronted by five or six Mexican soldiers who thought the Americans had crossed into Mexico. The Mexican troops reportedly removed a weapon from one of the American soldiers, who were traveling in an unmarked vehicle.

The U.S. soldiers were north of the border but south of a border fence, according to U.S. Northern Command, which said, “the U.S. soldiers were appropriately in U.S. territory,” and “followed all established procedures and protocols.”

While Trump suggested future U.S. troops at the border would be armed, the incident showed that at least some of the U.S. troops at the border are already carrying weapons, said Christopher Wilson, of the Wilson Center’s Mexico Institute.

“While the incident shows that mistakes can and do happen, rather than increasing tensions between the two militaries it emphasizes the importance of ongoing bilateral cooperation and communication more than anything else,” Wilson said, adding that, “communication between the troops from both countries led to a rapid de-escalation of what could have been a much more grave incident.”

Mexican President Andrés Manuel López Obrador promised at a Wednesday news conference to investigate the border incident.

"We are going to analyze this incident, we are going to take account of what he (Trump) is indicating and will act in conformity with the law, within the framework of our sovereignty," Obrador said.

He added: "We are not going to fight with the government of the United States. The most important thing is that we want a relationship of mutual respect and cooperation for development."

Trump recently backed off his threat to seal the entire border, citing Mexican cooperation.

The Associated Press and Leo Shane III, in Washington, D.C., contributed to this report.