"Our relationship with Saudi Arabia is important to this country, but that does not prevent us from putting forward robust views on these matters of grave concern", she said.
Both French President Emmanuel Macron and British Prime Minister Theresa May said they raised the Khashoggi case during private meetings with the crown prince, with Macron overheard on an open microphone telling him, "You never listen to me".
US intelligence agencies have evidence that Crown Prince Mohammed and al-Qahtani had 11 exchanges that roughly coincided with the hit team's advance into the Saudi Consulate in Istanbul, where Khashoggi was murdered. Two months later, Khashoggi was killed by Saudi operatives.
Prince Mohammed was visiting Algeria as part of a tour of Arab countries he has resumed after attending the G20 summit in Argentina on the weekend.
The Journal also reported on Friday that in August 2017 MBS had told associates if his efforts to persuade Khashoggi to return to Saudi Arabia were unsuccessful "we could possibly lure him outside Saudi Arabia and make arrangements".
Saudi authorities have vehemently denied the crown prince was involved.
Michelle Obama shocks NYC crowd with use of the S*** word
Michelle Obama doesn't seem like a woman who ever forgets where she is - she doesn't really have the luxury. "But sometimes that stuff doesn't work".
When he informed Khashoggi of this, the journalist replied, "God help us".
Bill Marczak, a research fellow at Citizen Lab, said there is high confidence Abdulaziz's phone was hacked by a Saudi-linked operator of NSO Group's Pegasus, an Israeli-made spyware.
Several US news reports say that the Central Intelligence Agency has concluded that the crown prince ordered the killing, even if there is no "smoking gun" evidence.
Analysts had been touting a Russia-Saudi deal ahead of talks next week in Vienna of the OPEC oil cartel, as global crude prices have been slumping.
Western nations are calling for an end to the Saudi-led military campaign in neighboring Yemen, which was launched by Prince Mohammed, as a humanitarian crisis there worsens.