The exact date of the secret talks remains unknown, but Patel, a deputy assistant to US President Donald Trump, went to Syria earlier this year, marking the first time since 2010 that such a high-level US official has met with the government of Syrian President Bashar Assad.
According to The Wall Street Journal, Patel was trying to secure the release of at least two Americans believed to be held citizen in Syria - Austin Tice, a former Marine and freelance journalist, and Majd Kamalmaz, a Syrian-American therapist.
In March, Trump said his administration was "working very hard with Syria" to get Austin Tice back to the US.
In August, US Secretary of State Mike Pompeo said that Trump wrote to Assad in March to propose direct dialogue on the missing journalist.
Tice disappeared in Syria in August 2012. The US government has offered a $1 million reward for information that could help with Tice’s release.