President Donald Trump announced Wednesday that he will return to the U.S.-Mexico border in three weeks to tout the construction of his promised border wall, his signature campaign promise.

Details about the trip — his fifth to the southwestern U.S. border as president — are still unclear.

Trump offered little other information when he made the announcement during a briefing about drug trafficking at the border.

"We're going to have a news conference at the border over the next three weeks," Trump said. "We're going to do it in areas where we're building large stretches of wall."

The White House declined to release any additional details, although there are only a few areas along the U.S.-Mexico border with ongoing or upcoming construction projects in the next few weeks to replace or build new physical barriers.

Those locations, according to the projects that U.S. Customs and Border Protection has announced so far, are: San Diego, where CBP is replacing 14 miles of secondary fencing; the Rio Grande Valley in Texas, where crews are clearing land for the first of 14 miles of new levee walls; and in Yuma, where construction is slated to begin in April to replace 14 miles of fencing.

Trump's most recent visit to the border was on Feb. 11, when he held his first re-election rally in El Paso, Texas. He was there for just a few hours and did not tour any of the border-enforcement facilities, although the location of his rally was within view of the border fence separating El Paso from Ciudad Juarez.

But his most high-profile visit was to San Diego on March 13, 2018, to tour eight border-wall prototypes, which have since been demolished.

Trump previously had visited the Rio Grande Valley on Jan. 10, where he met with troops deployed to the border, and a military base in Yuma on Aug. 22, 2017, on his way to Phoenix.

During the short portion of Wednesday's drug-trafficking briefing that was made public, Trump talked about the danger that drugs coming over the border — especially hard drugs like fentanyl — posed for Americans.

That's one of his main justifications for declaring a national emergency on Feb. 15 in order to free up $8 billion for the construction of a border wall, which he again claimed would help stem the flow of drugs.

As he has in the past, Trump once again contradicted his own administration's statistics and analysis showing that the vast majority of hard drugs are smuggled and caught at the ports of entry, which would not be impacted by the wall construction.

"We have tremendous amounts of technology going into the ports of entry, where a lot of the drugs come in," Trump said. "But I think it's highly overrated.

"I think much of the drugs, the big loads of drugs and certainly the human traffickers go, not through the ports of entry, they go to the open areas where they don't have walls," he added, although he offered no evidence to back those claims.

Trump also touted the investment of millions of dollars in technology at the ports of entry, which he said would stop drug trafficking. However, Customs and Border Protection has routinely pointed out the ever-changing methods smugglers try to get drugs through the border crossings.

On Jan. 26, customs officers working at the Mariposa commercial crossing in Nogales discovered 254 pounds of fentanyl hidden in a shipment of cucumbers. That's the largest fentanyl seizure ever made at any port or border crossing.

Customs officers used an X-ray machine to detect hidden compartments in the floor of the tractor-trailer; a canine officer then detected the odor of the drugs inside.

Trump said that investments in technology at the ports of entry would only work if they are complemented with the construction of his long-promised border wall.

He added that later this week, his administration would announce another major contract for the construction of additional physical barriers along the U.S.-Mexico border.

Since the start of Trump's presidency, construction crews have completed the replacement of more than 26 miles of border fencing in three separate projects totaling $113 million.

Two others projects are currently ongoing, including the start of construction for new levee-wall fencing in areas that previously didn't have any. Work is also slated to begin on three additional projects in the coming months.