Days after his inauguration last year, Mr. Trump ordered construction to begin immediately on a border wall. Customs and Border Protection then created a process to help decide where a wall was most needed on the border, and for how many miles.

“The U.S. Border Patrol has been very clear that a border wall is essential to gaining operational control of the Southwest border,” said Benjamine Huffman, the chief of the Border Patrol’s strategic plan and analysis directorate. “The fact is, when it comes to border security, the border walls system works. Suggestions that the Border Patrol believes otherwise are false.”

The Senate Democrats’ report comes as Mr. Trump is stepping up his calls for building a border wall. On Monday in New Hampshire, where he outlined plans to fight opioid abuse, the president again said that building a wall would block drugs from entering the United States. “We’ll build the wall to keep the damn drugs out,” he said.

Last year, Customs and Border Protection spent $20 million on border wall prototypes near San Diego. Agency officials said they have been testing the mock-ups to decide which best curbed illegal immigration and drug trafficking.

Congressional Democrats and some Republicans, including Representative Will Hurd of Texas, have questioned the need for a wall and instead called for more technology along the border, such as sensors and surveillance equipment. A February 2017 study by the Government Accountability Office found that Customs and Border Protection had not shown the extent to which fencing and walls have secured the border.

The House on Thursday approved spending money on border fencing, but not a border wall. The bill would fund nearly $1.6 billion for border security, including technology and repairs to existing barriers. That includes $641 million for about 33 miles of new border fencing in the Rio Grande Valley.

The administration wants to spend $18 billion over the next 10 years to build a wall on nearly 900 miles of the Southwest border. Currently, there are nearly 700 miles of wall and fences on the border.