President Donald Trump’s encounter with Russian President Vladimir Putin could be the catalyst for major diplomatic progress over Syria, one expert told CNBC Monday.

The first official dialogue between the two global leaders will take place in Helsinki’s presidential palace on Monday, marking a symbolic end to the Western effort to isolate Russia after its 2014 annexation of Crimea.

Ahead of the summit, neither side has sought to ramp up expectations of the meeting. And most external observers expect Trump and Putin to simply exchange warm words with one another, before potentially agreeing to a tentative deal to start talks on issues such as nuclear arms control and Syria.

“I think that along with bi-lateral arms control between Russia and the United States, Syria is quite likely today to be one of the top subjects,” Christopher Granville, Russia expert and managing director at TS Lombard, told CNBC’s “Squawk Box Europe” on Monday.

He explained that since Trump’s election, U.S. and Russian military forces have been working together “pretty closely” in the Syrian theater, marking a “complete change” to the previous Obama administration.

“So I think there is quite interesting scope for a significant breakthrough,” Granville added.