Gulf OPEC producers Saudi Arabia and Kuwait are between them boosting crude supplies by more than 200,000 barrels per day (bpd) this month, lifting total cartel output to 30.2 million bpd for May, an OPEC source told Reuters on Wednesday.

Overall output from the 11-member producer group may swell to 30.5 million bpd from July as the cartel seeks to accelerate its stockbuilding drive to meet higher winter demand, he said.

Saudi Arabia now is pumping 9.65 million bpd, up about 150,000 bpd from April, the source said. Production from Kuwait is running at 2.65 million in May versus around 2.58 last month, he said. Core Gulf OPEC producers have steadily raised production since mid-March to build global oil stockpiles ahead of an anticipated demand surge in the fourth quarter.

Their efforts are expected to intensify from July, when cartel output may rise to 30.5 million bpd, the source said.

Top world oil exporter Saudi Arabia could provide a significant portion of the extra 300,000 bpd, he said.

The kingdom”s official output capacity is 11 million bpd.