On Wednesday, President Barack Obama delivered a nationally televised speech promising to destroy the extreme terrorist group known as the Islamic State or ISIS. One strategy he proposed is by arming moderate Syrian rebels who are fighting against the Syrian regime and against ISIS.

However, while the United States begins to strengthen its ties with Syrian rebels, it's been reported that one of the rebel groups agreed to a cease-fire with ISIS on Friday.

According to the Syrian Observatory for Human Rights, a group monitoring the civil war in Syria, Jihadists from the Islamic State have struck a non-aggression pact with moderate and Islamist Syrian rebels in Hajar al-Aswad, a suburb of Damascus, reports the Daily Mail.

Under the deal, "The two parties will respect a truce until a final solution is found and they promise not to attack each other because they consider the principal enemy to be the Nussayri regime," reports the Agence France-Press (AFP). Nussayri is a derogatory term used to describe President Bashar al-Assad's Alawite ethnic group, which is an offshoot of Shiite Islam.

Some sources also say that a major U.S. ally linked to the Free Syrian Army is part of the group of moderate and hardline rebels that have agreed not to fight with ISIS in order to focus on overtaking the regime of Syrian President Bashar Assad.

The deal comes as it was revealed that ISIS is suffering from a dramatic drop in their oil revenue from black-market sales after many engineers abandoned the oil fields.

There are some reports that the terrorist group was raking in up to $3 million a day over the summer from oil fields that they have seized.

However, Michael Stephens from the Royal United Services Institute think-tank says, "Revenues are down below $1.5 million a day now," The Times reports.

"I can see Isis running out of oil down the line. They are not at that point yet -- production in Syria is still pretty stable -- but I think they're in trouble," he said.

The dip in their revenue could plummet even more if the United States launches airstrikes on key ISIS strongholds in Iraq and Syria.

Furthermore, news that the Syrian Revolutionary Front, a major player in the U.S. moderate coalition, has now chosen to stop fighting ISIS may inspire other groups to team up with ISIS.

"Given reports that Assad avoided fighting ISIS in order to crush the moderate rebels -- his calculus being that the West would eventually combat the extremists, as it is now doing -- potential U.S. partners may decide that instead of being prey to both extremists and the government, they should settle one battle," reports the AFP.