U.S. Defense Secretary Jim Mattis has told Arab leaders that Russia is no replacement for the United States in the Middle East, following Moscow's military intervention in Syria.
"Russia's presence in the region cannot replace the long-standing, enduring, and transparent U.S. commitment to the Middle East," Mattis said on October 27 at a meeting in the Bahraini capital, Manama.
Later on October 27, Russian President Vladimir Putin is due to attend a summit in Istanbul with the leaders of France, Germany, and Turkey seeking to find a lasting political solution to the seven-year civil war in Syria.
Russia supports the regime of Syrian President Bashar al-Assad. Turkey backs the rebels seeking to oust the Syrian leader.
Mattis told the annual Manama Dialogue security conference in Bahrain that Moscow's "opportunism and willingness to overlook Assad's criminal activities against his own people evidences its lack of sincere commitment to essential moral principles."
Mattis said Iran's support for the Syrian regime "coupled with Russia's repeated vetoes of UN Security Council resolutions, is the leading reason Assad remains in power."
In his remarks, Mattis also warned that incidents like the killing of Saudi journalist Jamal Khashoggi undermined Middle Eastern stability and that the United States would take additional measures against those responsible.
Khashoggi, 59, a U.S. resident and Washington Post columnist, was critical of Saudi rulers. He disappeared after walking into Saudi Consulate in Istanbul on October 2 to obtain marriage documents.
Turkey alleges a 15-member "hit squad" was sent to kill the journalist.
Saudi Arabia has said it arrested 18 people in connection with Khashoggi's killing.
Saudi Arabia's public prosecutor said on October 25 that the killing of Khashoggi was premeditated, reversing previous official statements that his death was unintended.
The United States "does not tolerate this kind of ruthless action to silence Mr. Khashoggi, a journalist, through violence," Mattis said at the meeting in Manama.
"The failure of any nation to adhere to international norms and the rule of law undermines regional stability at a time when it is needed most,” he added.
He did not mention de facto Saudi ruler Crown Prince Mohammed bin Salman who has faced international criticism, with many officials charging he must have known about Khashoggi's killing, and some saying he may have ordered it.
U.S. Secretary of State Mike Pompeo this week announced moves against 21 Saudis to either revoke their visas or make them ineligible for U.S. visas after the Khashoggi killing.
"Our secretary of state has already revoked visas and will be taking additional measures," Mattis said.
Speaking at the conference in Bahrain, Saudi Foreign Minister Adel al-Jubeir said Riyadh will prosecute the suspects in the killing of Khashoggi.
"On the issue of extradition, the individuals are Saudi nationals. They're detained in Saudi Arabia, and the investigation is in Saudi Arabia, and they will be prosecuted in Saudi Arabia," Jubeir said in response to a call by Turkey for extradition.
He said the kingdom has made it "very clear that those responsible will be held responsible" while calling the global outcry over Khashoggi's killing "hysterical."
Turkish President Recep Tayyip Erdogan has called for the extradition of the 18 Saudi nationals who authorities say were involved in the murder of Khashoggi.
Erdogan has also called on Saudi Arabia to disclose the location of Khashoggi's body.