Saudi Crown Prince Mohammed bin Salman has garnered international attention with his reforms and rapid rise to power

Saudi Arabia's diplomatic brawl with Canada has exposed what Western officials call "new red lines" in their engagement with the oil-rich kingdom, deterring nations from publicly criticising its human rights record.

A furious Saudi Arabia last month expelled Canada's ambassador and froze all new trade after Ottawa denounced a crackdown on activists in the Gulf state, in an increasingly combative approach to international censure.

Canada has refused to give ground, vowing to always stand up for human rights globally, even as diplomats say high-level negotiations are ongoing between the two countries to resolve differences.

But Canada appears to be standing alone.

"We are coming to terms with the new red lines," said a Western official, explaining why hardly any allies have vocally backed Canada's stance.

"We are trying to understand: Can we still do critical tweets from foreign ministries in our capitals? What's going to get you PNG'd?" the official added, referring to the expelled Canadian envoy being declared persona non grata by the kingdom.

Major Western powers including the United States -- a key ally of Saudi Arabia -- have not publicly asserted support for Ottawa.

Last month, the European Union had planned to release a public statement effectively backing Ottawa's position on human rights, a Western source told AFP.

But the plan was dropped, with European and EU ambassadors instead delivering a "demarche" -- a formal diplomatic note -- in a private meeting with Saudi Foreign Minister Adel al-Jubeir.

"Western countries will very much be wary of openly criticising Saudi domestic policy," Bessma Momani, a professor at Canada's University of Waterloo, told AFP.

"The Canadian case has proved that lots of business deals could be lost if criticism of Saudi Arabia upsets its rulers."

Spain on Thursday said it will sell 400 laser-guided bombs to Saudi Arabia, involved in a ruinous bombing campaign in Yemen, after initially blocking the 2015 deal.

The U-turn comes after reports emerged that Riyadh was considering cancelling a 1.8-billion-euro warship contract with Spain -- a deal that involves 6,000 jobs in a country with one of Europe's highest unemployment rates.

- 'Silence is deafening' -

Analysts say it illustrates how Saudi Arabia is increasingly using its economic muscle to quell foreign criticism under its young de facto leader, Crown Prince Mohammed bin Salman.

And it appears to be succeeding.

"The prince has definitely tamped down criticism of Saudi domestic and... foreign policy particularly with regards to Yemen, since the kerfuffle with Canada," said Momani.

"The silence of Canadian allies is deafening."

The row with Ottawa erupted after an Arabic language tweet on August 5 from the Canadian embassy in Riyadh -- calling for the "immediate release" of activists jailed in the kingdom -- infuriated the Saudi government.

At a press conference last month, Jubeir did not specify the kingdom's exact demands for Ottawa, insisting only that Canada's perceived interference was a "big mistake".

Multiple Western officials said Canada was asked to delete that tweet, which in Arabic is seen to have the potential to go viral in the kingdom, an absolute monarchy known for its tightly controlled public messaging.

While the message was also tweeted in English, a Western official said the Arabic version was interpreted locally as an attempt to "communicate directly" with Saudi people -- a serious infraction in the eyes of the kingdom.

Canada refused to delete it, the sources told AFP, and the embassy's once low-profile Twitter account has seen its following jump from a few hundred to more than 12,000.

The contentious Arabic message has seen thousands of retweets.

- 'Megaphone to shout criticism' -

Saudi officials privately insist that polite, closed-door engagement is a more effective diplomatic tool than public denunciations of the kingdom, long condemned for its human rights record.

"Using a megaphone to shout criticism may not work," another Western official told AFP.

"But who in the (Saudi) government do we talk to about human rights? There are no clear channels of engagement."

The Saudi information ministry's Centre for International Communication did not respond to a request for comment.

In recent weeks, the kingdom has detained a number of human rights and women campaigners, some of them accused of undermining national security, with scant public information about their whereabouts or the legal status of their cases.

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