The Syrian regime of President Bashar Al-Assad “has nowhere left to go” and “cannot escape” international accountability, the former US special envoy for Syria said on Twitter just hours after his role ended with the inauguration of US President Joe Biden.

“From Washington, we see clearly that the Assad regime cannot escape the pressure of the Caesar Act [sanctions],” tweeted Joel Rayburn. “Nor can it overcome its international isolation. My message to Damascus at the end of my tenure is this: you have nowhere left to go.”

The former special envoy, who is also the former Deputy Assistant Secretary for Levant Affairs, added that the regime in Damascus had reached its limit and that it has “no choice but to accede to 2254.” This was a reference to the UN Security Council resolution in 2015 that called for a ceasefire, political solution and transition in Syria.

In a video he posted separately, Rayburn said that he will hope and pray that the Syrian people would one day experience “that same joy and pride in a peaceful transition of power” as he felt in the transition of the presidency from Donald Trump to Joe Biden.

Rayburn’s stepping down from his role at the State Department this month was, he clarified last week, not due to any personal or political reasons. “[It is] a normal rotation of personnel that happens during a transition from one administration to another.”

Biden has not yet appointed a new special envoy for Syria, but concerns have already been raised over his administration’s resemblance to its predecessors, which had interventionist foreign policies for the Middle East.