Warning comes after Turkish leader reached agreement with Putin for removal of Syrian Kurdish fighters in area; also repeats threat to send refugees to Europe

Experts doubtful whether new plans to secure oil fields amid troop withdrawal are realistic, or even legal

Deployment will likely include tanks; Esper does not give details on troop numbers but says despite Trump vow to bring soldiers home, many will be repositioned

300 military police and 20 armored vehicles sent to patrol areas along the border with Turkey and oversee the pullout of Syrian Kurdish fighters

Turkey and Kurdish-led SDF also fighting despite truce; clashes underscore risk of spiraling violence as multiple armies jostle for position in volatile border region

Defense Department announcement comes as Trump draws criticism for vowing to protect Syria's fuel reserves even as he heralds withdrawal of American troops

'We demand and agree to this,' says commander of Syrian Democratic Forces of proposal, which would require UN approval

US president ceded American influence over large part of the Middle East to rivals, plunging region into uncertainty

But, he says, Washington hasn't seen widespread evidence of ethnic cleansing; defense secretary says Turkey 'heading in wrong direction' after Trump announces lifting of sanctions

'Let someone else fight over this long, blood-stained sand,' president says; Critics charge move leads to loss of US influence in area and will see Islamic State resurgence