And so in the end, a world of warnings failed to persuade Donald Trump to swerve.

Neither the pleas of churches nor of mosques; nor of the Pope; nor of Turkey, Egypt or China. None of their words of intervention mattered.

What had been warned against in many international quarters and described as reckless, irresponsible —  even as "diplomatic arson" — is having immediate consequences that are just as global in scope.

In Israel, Trump's few, long-awaited words Wednesday recognizing Jerusalem as Israel's capital are being celebrated as historic and courageous.

Elsewhere, Trump's unilateral declaration on a place revered as holy by millions around the world — on an incendiary issue long delicately handled by countless diplomats and world leaders — has brought, in the words of UN Secretary General Antonio Guterres, "a moment of great anxiety."

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Men walk past the Dome of the Rock at the Al-Aqsa mosque compound — known to Jews as the Temple Mount. Both Israelis and Palestinians claim Jerusalem as their capital. (Chris McGrath/Getty Images)

That declaration has already been met with protests in several countries — from Jordan to Turkey — and swift denouncements even from some of the U.S.'s staunchest allies.

"We disagree with the U.S. decision," British Prime Minister Theresa May said in a blunt statement Wednesday. "We believe it is unhelpful in terms of prospects for peace in the region."

An avalanche of condemnations of what Trump called a "recognition of reality" also came swiftly online: from ordinary people and veteran Middle East watchers alike.

"#Trump is doing a truly *excellent* job at destroying what remains of U.S. credibility in the #middleeast," tweeted Charles Lister of the Middle East Institute, a Washington, D.C.-based think-tank.

"Grim days ahead."

3 'days of rage'

In the immediate wake of the announcement comes the head-on impact on what little life was left in the mostly moribund peace process between Israelis and Palestinians.

This may well be a final blow.

A blow, too, Palestinians and others believe, to the claim the U.S. could still have a role to play in bridging the vast chasm between the two sides — despite assertions from Trump and Israeli Prime Minister Benjamin Netanyahu to the contrary.

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Palestinians burn posters depicting Israeli Prime Minister Benjamin Netanyahu and U.S. President Donald Trump during a protest Wednesday in Rafah, in southern Gaza, against the U.S. recognizing the city of Jerusalem as the capital of Israel. (Ibraheem Abu Mustafa/Reuters)

Protests had already started prior to the announcement, with Palestinians declaring three "days of rage." In Gaza on Wednesday, protesters set pictures of Trump ablaze.

Those protests have the potential to snowball — and that's just part of what the world will have to contend with in the coming days, and possibly longer.

Trump's words will strain pivotal diplomatic relationships, widening the rift with Europe and striking discord with governments from Turkey to Canada, where the minister of global affairs said in a statement that the status of Jerusalem "can be resolved only as part of a general settlement of the Palestinian-Israeli dispute."

Trump's words will also compound anti-American sentiment and possibly even fuel extremists in the long term.

All reasons that his words could inject instability in places well beyond Old Jerusalem's city walls.

Trump 'declaring war'

At the time of writing, protests have been called for in Los Angeles, London, Manchester and Dublin. One has also been planned for Thursday in front of the U.S. Embassy in Amman, Jordan. In Turkey, protesters gathered at the U.S. consulate shortly after the announcement.

U.S. embassies have warned citizens of the possibility of protests that could turn violent in Germany, Italy and Portugal. 

Trump's move could also exacerbate and widen another chasm — between the West and Muslim countries — that benefits extremists on all sides.

Already incensed by Trump's travel ban on six majority-Muslim countries and years-long wars in Iraq, Syria and Afghanistan, many Muslims will see this decision as an affront and as an extension of an anti-Muslim policy.

Trump is "declaring war against 1.5 billion Muslims, hundreds of millions of Christians," said Manuel Hassassian, Palestinian chief representative in the U.K.

The issue of Jerusalem isn't only a Middle East one, its delicate status derived from more than just the tug of war between Israelis and Palestinians, each claiming it as their capital. It is also home to sites revered by Jews, Christians and Muslims.

'Ill-considered' decision

Divorced from the Israeli-Palestinian conflict, for Muslims worldwide, the Al-Aqsa mosque — on the site known to Jews as the Temple Mount — is a deeply emotional and sensitive matter, too. Passion about its fate reaches into homes from Calgary to Paris to Islamabad and beyond.

It is the religion's third-holiest site, after those in Mecca and Medina. 

In the region, while sentiments about the Israeli-Palestinian conflict have been dormant as other clashes have raged, Trump's stance will give them new life by touching a nerve on the grandfather of all Mideast causes.

Much of the indignation centred on Trump's decision flying in the face of international consensus on Jerusalem's status. 

Leaders of key U.S. allies — Saudi Arabia, Egypt and Jordan — publicly voiced their concerns about Trump's plans but are unlikely to take major steps to rupture a relationship that is crucial to them.

A Saudi royal court statement called the decision "unwarranted and irresponsible."

Trump's decision puts all U.S. allies in the region in an awkward position. It gives strength to anti-American voices like Iran's and Hezbollah's, which relish pointing out what they describe as the hypocrisy of Arab nations that outwardly express allegiance to the Palestinian cause and yet tacitly support U.S. policies.

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British Prime Minister Theresa May, seen here with Trump during the G20 summit in Hamburg in July, said Trump's statement was 'unhelpful in terms of prospects for peace in the region.' (Matt Cardy/Getty Images)

Jordan, which has a majority Palestinian population and whose king is the official custodian of the Al-Aqsa holy site, may well pay the biggest price in terms of stability.

The decision "would have dangerous repercussions for the security and stability of the Middle East," King Abdullah said in a statement before Trump spoke. "It would undermine the U.S. administration's efforts to resume the peace process and hurt the feelings of both Christians and Muslims." 

Jordanian officials later called the Jerusalem declaration "legally null."

Turkey, a NATO member, used stronger language, vowing to end its diplomatic ties with Israel if Trump went ahead.

Separately, the decision could swell support for militant organizations and embolden individuals who exploit the Palestinian cause to spread their own extremist and anti-Western ideology. Those consequences could linger for years, fuelling a fresh cycle of violence and hate.

The decision is "completely unhelpful at best, dangerously ill-considered at worst," said Rex Brynen, a professor of political science at Montreal's McGill University who specializes in the Middle East.

"I think it contributes to the constant drip, drip, drip of delegitimizing and demonizing the United States. It does damage to the U.S. in a lasting way."