Image caption Apple and Samsung have been locked in patent litigation for years

A ban on sales of older models of Apple's iPad and iPhone in the US has been overturned by the Obama administration.

In June, the US International Trade Commission (ITC) ruled that Apple infringed a patent of rival Samsung.

President Barack Obama's trade representative has now vetoed that decision because of its "effect on competitive conditions in the US economy".

Such a veto is a relatively rare event.

The patent related to 3G wireless technology and the ability to transmit multiple services correctly and at the same time. The ITC ordered a halt on all imports and sales on AT&T-sold models of the iPhone 4, iPhone 3, iPhone 3GS as well as the iPad 3G and iPad 2 3G. Some of those devices are no longer on sale in the US.

Such patents are called "standard essential patents" and they cover technology that must be used to comply with standards set by the industry as a whole.

Import-ban orders from the ITC are subject to review by Mr Obama, and he had 60 days to veto the decision.

His trade representative, Michael Froman, said that the administration was concerned about the use of essential patents in litigation.

Apple welcomed the news and applauded Mr Obama "for standing up for innovation". It added: "Samsung was wrong to abuse the patent system in this way."

Korea's Samsung responded: "The ITC's decision correctly recognised that Samsung has been negotiating in good faith and that Apple remains unwilling to take a licence."

Apple and Samsung are in the midst of a global patent war. Last year, a court ruled that Samsung owed Apple $1bn in damages for infringing Apple patents, an award that was later slashed to $598.9m.

An appeal in that case is due to be heard soon.