All global oil producers should help balance the market, OPEC’s Secretary General Mohammad Barkindo told reporters on Tuesday when asked what else the Organization of the Petroleum Exporting Countries could do to ease a global oil glut.

“It is beyond any group of stakeholders, it has to be a collective responsibility of all producers,” he told reporters on the sidelines of an industry conference in Istanbul.

OPEC and non-OPEC producers have the capacity to extend and deepen their production cuts should the oil market’s situation become even more complex, Russia’s Oil Minister Alexander Novak told CNBC on Monday.

“If necessary, we can extend the agreement. If necessary, we can increase the amounts that need to be reduced or on the contrary, we can move to reduce them,” Novak said, according to a CNBC translation, on the sidelines of the World Petroleum Congress in Istanbul.

In May, OPEC and allied non-OPEC members, such as Russia, agreed to cap oil production through to March 2018. However, despite OPEC and non-OPEC producers ratifying a deal to extend output cuts, prices have slumped.

Brent crude futures, the international benchmark for oil prices, have tumbled more than 9 percent since the announcement, in part because of the increased production levels of Nigeria and Libya – two OPEC members exempt from cutting output.