The decision was taken despite mounting calls to cooperate more closely with Russian President Vladimir Putin in the fight against Islamic State following the militant group's November 13 attacks in Paris which killed 130 people, Reuters wrote.
U.S. President Barack Obama, Germany's Angela Merkel, Britain's David Cameron, Italy's Matteo Renzi and French Foreign Minister Laurent Fabius, who represented President Francois Hollande at the summit, attended the brief meeting near the conclusion of the G20 meeting in Antalya.
The sanctions are due to expire in January, before full implementation of the so-called Minsk peace deal, which aims to resolve the standoff between Kiev and pro-Russian separatists in eastern Ukraine.
Western countries have said all elements of Minsk need to be fulfilled before they can consider easing the sanctions.
In particular, the diplomat said, the leaders had concluded that it was important to maintain pressure on Russia ahead of planned elections in eastern Ukraine.
"The elections in Ukraine are heavy lifting," the diplomat said, requesting anonymity because the agreement in Antalya was confidential.
"We only have a chance to get what we want if we play the sanctions card. Financial sanctions need to stay in place until the bitter end," the diplomat added.
