The rapid advance of rebels in Northwest Syria puts the US, which was "caught off guard," at risk, as well as other countries such as Turkey, Russia and Iran, said the former American ambassador James Jeffrey, quoted by Reuters, writes BTA.
Jeffrey, former US ambassador to the Coalition to Defeat the "Islamic State" from the previous Trump administration, said the US president-elect is likely to increase pressure on Syria's ally Iran, both there and across the region.
The rebel takeover of Aleppo and Hama is a blow to President Bashar al-Assad nearly 14 years after protests against him erupted.
"Such a dramatic shift in the balance of power in Syria worries everyone because each of the countries involved holds a piece of Syria," said Jeffrey, a former envoy to Turkey and Iraq who directs the Middle East Program at the Washington-based Center " Wilson".
"We found ourselves unprepared. We rely on our available intelligence capacity, so we have to rank our priorities," he said in a telephone interview.
About 900 US troops have been deployed mainly in northeastern Syria to support the Syrian Democratic Forces since the US intervention in 2014.
Asked about policy changes when Trump returns to the White House next month, Jeffrey said Trump's statements and past actions suggest he "will aggressively confront Iran throughout the region.
US national security adviser Jake Sullivan said this week that it was no surprise that the rebels would try to take advantage of the situation at a time when the attention and forces of Assad's main backers - Iran and Russia - are focused on conflicts in other regions.
Turkey, which is a member of NATO, Russia and Iran have troops in Syria. The rebels include some Turkish-backed groups led by Hayat al-Tahrir al-Sham, which Ankara and Washington consider a terrorist organization.