The United States, an ally of Saudi Arabia, has opposed moves by regional countries to normalise ties with Assad, citing his government's brutality during the conflict and the need to see progress towards a political solution.
When asked about the rapprochement, a State Department spokesperson said the U.S. "stance on normalisation remains unchanged" and that it would not encourage other countries to normalise ties with Assad.
ARAB LEAGUE SUSPENSION
The United Arab Emirates, another strategic U.S. partner, has led the way in normalising contacts with Assad, recently receiving him in Abu Dhabi with his wife.
But Saudi Arabia has been moving far more cautiously.
The Gulf diplomat said the high-ranking Syrian intelligence official "stayed for days" in Riyadh and an agreement was struck to reopen embassies "very soon".
One of the regional sources identified the official as Hussam Louqa, who heads Syria's intelligence committee, and said talks included security on Syria's border with Jordan and the smuggling of captagon, an amphetamine for which there is a thriving market in the Arab Gulf, from Syria.
Syria was suspended from the Arab League in 2011 in response to Assad's brutal crackdown on protests.
Saudi's foreign minister Prince Faisal bin Farhan Al Saud earlier this month said engagement with Assad could lead to Syria's return to the Arab League, but it was currently too early to discuss such a step.
The diplomat said the Syrian-Saudi talks could pave the way for a vote to lift Syria's suspension during the next Arab summit, expected to be held in Saudi Arabia in April.
The United Arab Emirates reopened its embassy in Damascus in 2018, arguing Arab countries needed more of a presence in resolving the Syrian conflict.
While Assad has basked in renewed contacts with Arab states that once shunned him, U.S. sanctions remain a major complicating factor for countries seeking to expand commercial ties.