Sen. Chris Murphy of Connecticut says Congress should spend nearly $1 billion in the next fiscal year to combat fentanyl trafficking because the overdose crisis “is unlike anything we have faced before.”

Mr. Murphy, a Democrat and chairman of the Senate Appropriations subcommittee on homeland security, said the Department of Homeland Security needs the funding to detect and seize the synthetic opioid at ports of entry and dismantle smuggling networks while preventing profits from reaching global criminal organizations.

Roughly 70,000 of the 107,000 overdose deaths in the U.S. were linked at least in part to fentanyl in 2021, the most recent year for which complete data is available.

The U.S. government says nearly all of the fentanyl supply flows out of Mexico, often in the form of counterfeit pills that are taken by addicted persons or unsuspecting users.

“Thousands of families across the country have lost loved ones to this low-cost, highly potent drug, and reducing its flow into the United States must be our top priority,” Mr. Murphy said. “My proposal would supercharge the Department of Homeland Security’s fight against fentanyl and ensure it has the resources to do everything humanly possible to disrupt the trade and keep families safe.”

A large chunk of the funding would be devoted to hiring and deploying 500 additional Customs and Border Patrol officers at ports of entry and purchasing equipment to scan incoming vehicles. Mr. Murphy wants to increase the share of vehicles scanned from 40% to 65%.

About $300 million would be devoted to upgrading existing inspection equipment, bringing the total close to $1 billion, according to a breakdown by Roll Call.

President Biden has called on Congress to improve inspections at ports of entry. Democrats say most of the fentanyl that is reaching American streets comes through those entry points while Republicans say the administration is ignoring the amount that slips through unguarded portions of the border.

The parties are warring over a separate plan to permanently put fentanyl-related substances on the Schedule I list of drugs with a high risk of abuse, with Democrats wanting to shield persons convicted of quantity-based crimes from mandatory minimum criminal penalties.

Mr. Murphy said his plan should gather bipartisan support, however.

He said he looks forward to working with Sen. Katie Britt of Alabama, the top Republican on his subcommittee, to advance the plan. The senator released details of the proposal ahead of a Wednesday hearing on it before his panel.