The US Transport Security Administration has brought in a new set of rules for air cargo coming from five Muslim-majority Middle Eastern nations.
Cargo planes headed to the US from Egypt, Jordan, Qatar, Saudi Arabia and the United Arab Emirates will all face additional screening.
The decision was based on intelligence indicating potential bomb attacks, officials said.
The new rules will apply to all cargo on passenger or cargo-only flights.
A programme called Air Cargo Advance Screening (ACAS) - which is usually voluntary - will now be required for flights departing from the five countries.
"In close co-ordination with Customs and Border Patrol, I directed specific carriers to implement strict security requirements based upon recent information that established a need to implement additional security measures for air cargo bound to the United States," TSA administrator David Pekoske told CBS News.
Affected airlines will send US authorities information about the cargo they intend to carry in advance. Types of information covered by the scheme include shipping records - which could point authorities towards anomalies.
All cargo on commercial flights already undergoes security screening. The advance procedures may, however, help to flag certain items for secondary examination.
One example given to CBS News by officials was that of a $100 printer already available on the US market being shipped to the US at a cost of $500 from a country known to have some terrorist activity. Such an item might raise a warning.
Many airlines already voluntarily comply with the ACAS protocol - but it will now be mandatory for cargo from the five countries.
Airports affected include:
- Cairo International Airport (Egypt)
- Queen Alia International Airport (Jordan)
- King Abdul-Aziz International Airport (Saudi Arabia)
- King Khalid International Airport (Saudi Arabia)
- Doha International Airport (Qatar)
- Dubai International Airport (UAE)
- Abu Dhabi International Airport (UAE)
Airlines affected include Egypt Air, Royal Jordanian, Saudia, Qatar Airways, Emirates and Etihad.
The US government shutdown - which has left many federal agencies unstaffed - means that no formal written statement has been published on the TSA's website.
The move is the latest strengthening of safety procedures targeted at specific countries flying to the US.
In March 2017, the US - followed quickly by the UK - introduced a ban on laptops and other electronic items being carried as hand luggage on flights from selected countries.