Mr. Khashoggi, a critic of the Saudi government, vanished on October 2 after visiting its consulate in Istanbul.
A number of sponsors and media groups have decided to pull out of this month's investment conference in Riyadh, dubbed Davos in the Desert, as a result of concerns over Mr. Khashoggi's fate.
Diplomatic sources have told the BBC's James Landale both the US Treasury Secretary, Steve Mnuchin, and the UK's International Trade Secretary, Liam Fox, might not attend the event.
A joint statement of condemnation is also being discussed by US and European diplomats if it is confirmed that Mr. Khashoggi was killed by Saudi agents.
The conference is being hosted by the kingdom's Crown Prince Mohamed bin Salman to promote his reform agenda.
If neither Mr. Mnuchin nor Mr. Fox attend, it would be seen as a huge snub by two of Saudi Arabia's key allies.
A spokesman for the UK's international trade department said Dr. Fox's diary was not yet finalized for the week of the conference.
President Donald Trump has said the US will inflict "severe punishment" on Saudi Arabia if the kingdom is found to be responsible for the death of Mr. Khashoggi.
MA/PR