President Donald Trump has threatened to destroy Turkey's economy if Turkey goes "off limits" after his surprise decision to pull US forces out of north-eastern Syria.

In a series of angry tweets, Mr Trump defended the move that could open the way for Turkey to launch an attack on Kurdish fighters across the border.

The withdrawal was heavily criticised even by Mr Trump's Republican allies.

Kurdish forces were key US allies in defeating the Islamic State in Syria.

The US has some 1,000 troops across Syria and about two dozen had been pulled out from the border area, according to a senior state department official.

The withdrawal was described by the main Kurdish-led group as a "stab in the back", and critics say it could facilitate an IS resurgence and leave Kurdish forces at risk of being attacked by Turkey, which regards them as terrorists.

But Mr Trump warned Turkey not to take advantage of his decision - which goes against the advice of senior officials in the Pentagon and state department - saying he could "destroy and obliterate" its economy.

Last year, the US raised tariffs on some Turkish products and imposed sanctions on top officials as relations between the two Nato countries worsened over a number of issues.

Turkish President Recep Tayyip Erdogan has said his aim is to combat Kurdish fighters in the border area and set up a "safe zone" for up to two million of the more than 3.6 million Syrian refugees currently living in Turkey.

The country's defence ministry tweeted later that the establishment of such a zone is "essential" for Syrians and for peace in the region. "All preparations for the operation have been completed," the tweet said in Turkish.

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In a statement, Pentagon spokesman Jonathan Hoffman said "the Department of Defense made clear to Turkey - as did the president - that we do not endorse a Turkish operation in Northern Syria".

Earlier, Mr Trump said it was time "to get out of these ridiculous Endless Wars, many of them tribal" and that "Turkey, Europe, Syria, Iran, Iraq, Russia and the Kurds will now have to figure the situation out".
In the place of clarity we only have President Trump's tweets and statements which appear to contradict him from both the state department and the Pentagon.

This morning he appeared to signal the start of a US troop pullout from Syria and seemed to be washing his hands of the country, implicitly giving a green light for a major Turkish incursion.

Now both the state department and the Pentagon say there is no major shift in US policy; that only a handful of US troops have been pulled back for their own safety, fearing some Turkish move. And they insist that this administration, including the president, stands firmly against any further Turkish move across the border.

So did the President act on a Twitter whim in the wake of his phone call with Turkey's President Erdogan, only to be appraised of the likely consequences afterwards by officials? This is an object lesson in how dysfunctional US foreign policy-making has become.

'Disaster in the making'

Senate Majority Leader Mitch McConnell, the top Republican in Congress, was among those who criticised the decision. He said a "precipitous withdrawal of US forces from Syria would only benefit Russia, Iran and the Assad regime".

In a statement, Mr McConnell also said a majority in the Senate voted in January for an amendment expressing concern about the threat posed by Islamist militant groups in Syria and support for a continued military presence, and that "the conditions that produced that bipartisan vote still exist today".

Lindsey Graham, another Republican senator and a close ally of the president, called the move a "disaster in the making", and said he would introduce a Senate resolution opposing the decision and calling for it to be reversed.

In other reaction:

Nikki Haley, former US ambassador to the UN, said the Kurds "were instrumental in our successful fight against" IS and that "leaving them to die [was] a big mistake"

House Speaker Nancy Pelosi said the president "must reverse this dangerous decision", described by her as "reckless" and "misguided"

Kino Gabriel, spokesman for the Kurdish-led Syrian Democratic Forces (SDF) - which occupy former IS territory in north-eastern Syria - told Arabic TV station al-Hadath that the move "was a surprise and we can say that it is a stab in the back for the SDF"

Brett McGurk, former US special presidential envoy for the coalition against IS, said the announcement demonstrated a "complete lack of understanding of anything happening on the ground"

Mr Trump's decision was announced by the White House late on Sunday after a phone call with Mr Erdogan. Turkey considers the Kurdish YPG militia - the dominant force in the SDF alliance - an extension of the banned Kurdistan Workers' Party (PKK), which has fought for Kurdish autonomy in Turkey for three decades.

Last December, Donald Trump's announcement of a "full" and "rapid" withdrawal of US forces from Syria set off a firestorm of criticism that culminated in the resignation of Defence Secretary James Mattis.

Mr Trump eventually backed down, but his opponents appear to have secured only a temporary victory. Like last time, Mr Trump made Sunday night's withdrawal announcement after a phone conversation with Turkish President Erdogan.

Unlike last time, there are fewer advisers within the White House positioned to dissuade the president. And also unlike last time, Mr Trump is currently in the middle of a congressional impeachment inquiry that could very well leave him fighting to stay in office during a Senate trial.

If that happens, he'll need all the Republican friends he can get. This move, however, has even Senate loyalists like Lindsey Graham and Mitch McConnell calling the president's judgement into question. The president is taking a big gamble at a delicate time. For whatever reason, he has decided the risk is worth it.