The government is "deeply concerned" by reports of UK weapons being used by the Saudi air force in strikes on civilian targets in Yemen, Boris Johnson has said.
But he said he did not believe the "threshold" had been crossed which would demand the suspension of arms sales to the Middle Eastern country.
It comes after ITV News uncovered evidence that British-made cluster bombs were being used in the civil war in Yemen - weapons banned by Britain in 2010.
Britain has been under pressure to halt military exports to Saudi Arabia, who are leading a regional coalition supporting the Yemeni government in fighting Iran-backed Houthi rebels, amid repeated reports of civilians being hit.
The United Nations released a report earlier this year detailing "widespread and systematic" attacks on civilian targets, which would be in violation of international humanitarian law.
Speaking on the BBC's Andrew Marr Show, the Foreign Secretary said there were "very difficult questions" for ministers on the use of UK-built weapons and technology - but said he did not believe any law had been broken.
He confirmed British experts had been giving "general advice" to the Saudis on avoiding civilian casualties, but said they were not involved in selecting targets.