U.S. Vice President Mike Pence and Secretary of State Mike Pompeo are in Turkey seeking to secure a cease-fire in the Turkish invasion of northern Syria as President Donald Trump defended his decision to withdraw troops from the area, saying it's 'not our border' and that the Kurds are 'not angels.'

'Our mission set is to see if we can get a cease-fire, see if we can get this brokered,' Pompeo told reporters on his plane.

Pence and Pompeo, who traveled on different planes, intended to hold talks on October 17 in Ankara with Turkish President Recep Tayyip Erdogan, although it was not immediately clear whether Erdogan would agree to meet with them.

Trump said he believed Pence and Pompeo will 'have a successful meeting' in Turkey after a weeklong offensive that Ankara launched saying it wanted to clear the area of Kurdish forces and establish a buffer zone to resettle Syrian refugees.

Turkey's move came after Trump's abrupt decision announced last week to withdraw U.S. forces from northeast Syria, where they had been supporting Kurdish fighters battling the Islamic State (IS) group.

Turkey has long argued the Kurdish fighters in Syria are an extension of the Kurdistan Workers Party (PKK), which has waged a guerrilla campaign inside Turkey since the 1980s and which Ankara, Washington, and the European Union have designated as a terrorist organization.

If the talks fail, 'the sanctions, tariffs, other things that we're doing -- will do and are doing -- to Turkey will be devasting to Turkey's economy,' Trump said at a news conference alongside Italian President Sergio Mattarella in Washington.

But he said that the PKK 'is probably worse at terror and more of a terrorist threat in many ways than' IS.

Trump added that Kurds 'know how to fight and as I said, they aren't angels. They are not angels, if you take a look.'

Trump defended his decision to redeploy about 1,000 U.S. soldiers from northern Syria as 'strategically brilliant' for the United States, while saying he had no problem if Russia helped Syria in a conflict with Turkey.

Separately on October 16, a letter was disclosed in which Trump both cajoled and threatened Erdogan last week, urging him to act only in 'the right and humane way' in Syria.

In the letter, dated October 9 -- the day Turkey launched the invasion -- Trump wrote to his Turkish counterpart: 'Don't be a tough guy. Don't be a fool.'

The House of Representatives condemned Trump's pullout in a resolution that received an overwhelming majority of 354 votes, including 129 from Trump's fellow Republicans.

Kurdish Syrian civilians flee the town of Kobani on the Turkish border on October 16.

Since the U.S. troop withdrawal, the former U.S.-allied Kurds in northeastern Syria have teamed up with Syrian President Bashar al-Assad's forces and his ally, Russia, which has stepped in as the biggest power player, sending in patrols to the northern part of the country.

Meanwhile, German Chancellor Angela Merkel again called on Turkey to stop its military offensive in Syria.

Merkel told parliament on October 17 that the offensive strengthened the role of Russia and Iran in the region and that the consequences of that 'cannot be judged today.'

She said the military operation 'makes tens of thousands, among them thousands of children, flee,' calling it 'a humanitarian drama with big geopolitical consequences.'

In Budapest, Prime Minister Viktor Orban warned that Hungary would have to 'use force' at its southern border with Serbia if Turkey delivered on a threat to open the gates for refugees through the Balkans toward Europe.

Orban built a steel fence on Hungary's border with Serbia in 2015 to seal off the Syrian refugees' Balkan route of migration, used by hundreds of thousands of people fleeing the conflict to get to Western Europe.

Turkey, which hosts 3.6 million Syrian refugees, threatened to 'open the gates' to allow those already in the country to head for Europe if the EU portrayed Turkey's incursion into northeast Syria negatively.

'The next weeks will decide what Turkey does with these people,' Orban told private broadcaster HirTV in an interview late on October 16.

'If Turkey sets off further hundreds of thousands on top of this, then we will need to use force to protect the Hungarian border and the Serbian-Hungarian frontier and I do not wish for anyone that we should need to resort to that,' Orban said.

Orban's nationalist government has forged close relations with Russia, Turkey, and China.

Erdogan is due to visit Budapest early next month.

With reporting by AP, Reuters, AFP, dpa, and the BBC

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