Associated Press is reporting that China has cut the number of permits for rare earths mining in a new move to tighten controls over the exotic minerals needed to manufacture mobile phones, electric cars and other high-tech goods. The move appears to be aimed at tightening the political screws on Japan – the Japanese and Chinese governments are in a dispute now over a group of uninhabited islands in the East China Sea.

It’s not the first time this has happened. China temporarily suspended rare earths shipments to Japanese firms the last time tensions over the islands erupted two years ago.

Beijing has alarmed global manufacturers by restricting production and exports while it tries to build up its own processing industry to capture profits that flow to U.S., Japanese and European companies that use rare earths to make lightweight magnets, batteries and other products, Associated Press points out.

China has about 30 percent of world supplies of rare earths but accounts for more than 90 percent of production, the news agency reports. Its trading partners say quotas and taxes push up rare earths prices abroad, giving buyers in China an unfair advantage, it adds.

Meanwhile, Reuters and the Globe and Mail are reporting that on Saturday China’s ambassador to Canada warned Canada against letting domestic politics drive the Canadian government’s decision on whether to approve a Chinese state-owned oil company’s proposed $15.1 billion takeover of Calgary-based Nexen Inc.

“Business is business. It should not be politicized,” Ambassador Zhang Junsai said in an interview with Canada’s Globe and Mail newspaper.

“If we politicize all this, then we can’t do business,” he added. That was in reference to the Canadian government’s review of China’s proposed purchase of the Canadian oil and gas producer.

The deal, if completed, would mark the first outright takeover of a large Canadian energy producer by a Chinese state-owned enterprise, Reuters pointed out.