According to the source, it is currently unclear if the leaders will eventually sign the document.
The G20 summit started in the Argentine capital of Buenos Aires on Friday and will last through Saturday.
READ MORE: Merkel, Trump to Meet on Saturday on Sidelines of G20 Summit — German Government
Prior to the summit, Russian G20 Sherpa Svetlana Lukash said late November that negotiations to formulate the text of the joint declaration were likely to be complicated in light of "certain disappointment" with the results of Asia-Pacific Economic Cooperation (APEC) summit.
On November 17-18, the APEC summit was held in Papua New Guinea, and for the first time since 1993, it ended with no formal joint declaration signed over disagreements on some controversial issues related to the US-Chinese trade war.