U.S. special forces are slated to arrive in Syria "very soon," as promised by President Barack Obama's administration, to "suffocate and strangle" the core of ISIS, presidential envoy for the global coalition to counter ISIS Brett McGurk said Sunday.

McGurk, speaking on CBS' "Face the Nation," confirmed that Obama's administration will follow through on their promise made in late October to send no more than 50 special troops to advise allied forces in their fight against ISIS, but declined to say when the special forces would arrive in Syria.

"We're going to pressure them [ISIS] and strangle them in the core. And that means all around Iraq and Syria. And we're doing that by cutting offer their final 98-kilometer [nearly 61 miles] stretch of border they have with Turkey," McGurk said, adding that troops were working on cutting off links between Raqqa and Mosul (two cities under ISIS control) and "working with Iraqi security forces to retake Ramadi."

He also noted that local forces had conducted "a very successful operation" against ISIS, and added that the U.S. will also battle the international networks of the militant group, reported The Guardian. He revealed that local forces had captured about 435 square miles of lost territory and killed about 300 ISIS fighters while doing so within the last two weeks.

These comments came after Syrian President Bashar al-Assad said that his forces have been advancing on "nearly every front" in Syria's four-year civil war thanks to the airstrike campaign Russia began in September.

"After the participation of the Russian air forces in fighting terrorism, the situation has improved in a very good way, and now I can say that the army is making advancement in nearly every front, although front is not very precisely defined, it's not wrong, but let's say in many different directions and areas on the Syrian ground," Assad said an interview on Hong Kong-based channel Phoenix TV Sunday, according to TASS news agency. 

Obama, while speaking at an Association of Southeast Asian Nations summit in Malaysia on Sunday, asked Russia to rethink its strategy in Syria and focus on ISIS, arguing that Russian President Vladimir Putin has realized that ISIS "poses as greater threat to them than anything else in the region."

"The question at this point is whether they can make the strategic adjustment that allows them to be effective partners with us and the other 65 countries who are already part of the counter-ISIL campaign. And we don't know that yet," Obama said.