A US International Trade Commission judge, in a preliminary ruling, said Samsung infringed four of Apple’s intellectual property patents.
The patents include one that relates to the front face of the iPhone and one for touch-screen technology.
It is another win for Apple, after it was awarded $1.05bn (£652m) in damages by a jury in a separate case in August.
The ITC can block the import of products into the US.
The judge’s ruling will go in front of a full commission, which is scheduled to conclude its investigation in February.
Judge Thomas Pender agreed that Samsung violated four of Apple’s patents, but was not in violation of two others listed by Apple in the complaint.
Three of the patents are related to software features, while one covers Apple’s hardware.
However, the Samsung products in this case do not include its latest devices, limiting the impact of a potential import ban into the US.
Samsung has repeatedly argued that any sales ban would limit choice and raise prices for consumers in the US.
Apple and Samsung have bought legal cases against each other in more than 10 countries, each accusing the other of violating patents, as the two battle for market share in the hugely lucrative mobile industry.