US sanctions on Khashoggi killers 'weeks away'

US Secretary of State Mike Pompeo has said it may take "a handful more weeks" before Washington has enough evidence to impose sanctions on individuals responsible for the killing of Saudi journalist Jamal Khashoggi.

The murder has placed a strain on the decades-old alliance between the United States and Saudi Arabia.

"We're continuing to understand the fact pattern," Pompeo said on Thursday during an interview with Missouri-based KMOX news radio.

"We are reviewing putting sanctions on the individuals that we have been able to identify to date that have - that were engaged in that murder.

"It'll take us probably a handful more weeks before we have enough evidence to actually put those sanctions in place, but I think we'll be able to get there," he said, adding that US President Donald Trump had vowed accountability for all involved in the "heinous crime".

The top US diplomat had previously said the killing "violates the norms of international law".

But Pompeo emphasized, as Trump has, that "not only do we have important commercial relationships, but important strategic relationships, national security relationships with the Kingdom of Saudi Arabia, and we intend to make sure that those relationships remain intact".

Saudi Arabia's former intelligence minister, Prince Turki bin Faisal al Saud, said on Wednesday that the outcry in the US demonizing Saudi Arabia over Khashoggi's killing threatened to disrupt strategic ties between the two countries.

"We value our strategic relationship with the United States and hope to sustain it. We hope the United States reciprocates in kind," said Prince Turki, a royal family member.

Khashoggi, who lived in the US and wrote columns for The Washington Post, went to the Saudi consulate in Istanbul on Oct 2 to collect some documents, but he never reappeared. Riyadh initially denied any role in his disappearance, but under pressure from Turkish authorities it eventually identified 18 suspects in the case.

Riyadh said they will face justice in the kingdom. Ankara has repeatedly called for them to be extradited to Turkey for trial. Turkey pressed Saudi authorities on Thursday to tell them the whereabouts of Khashoggi's body, which has not been recovered

Speaking at a journalism awards ceremony on Thursday, Fred Ryan, the publisher and CEO of The Washington Post, which Khashoggi wrote for, urged the US government to take a tougher line.

"When officials of our government are asked about consequences for Jamal's murder, they often talk about 'balancing our interests in the area'," he said.

AP and Reuters contributed to this story.