Tension between China and its trading partners over access to key strategic minerals look set to increase after controversial calls last week from a mainland mining executive for more barriers to mainland exports of precious metals. 'The government should do more to preserve our precious natural resources,' said Yang Huanwen, deputy secretary-general of the Nonferrous Metals Society of China. In an interview with the South China Morning Post on Friday, Mr Yang called for barriers to be raised against new entrants into the mainland mining industry, tighter restrictions on exports, and the accumulation of strategic reserves of metals and minerals that were important to the nation's defence industry. 'Disordered competition among domestic mining companies, particularly small-scale, privately owned companies, has led to great damage to many metals and rare earth mines,' said Mr Yang, adding that this unregulated competition had also led to pollution and a waste of resources. In order to promote better administration of resources and more efficient mining, the government should raise entry barriers to mining firms or even prohibit private companies from taking part in the mining of strategic metals, he said. He also called on the government to follow the example of developed countries such as the United States and Japan to set up strategic reserves of metals and rare earth that were crucial to the nation's economy and national defence industry. 'Many rare metals and rare earth materials are key to the economy and national defence industry. 'China should build up a system to protect such valuable resources, as growing production for export has resulted in more pollution and low utilisation of the resources,' Mr Yang said. The controversial comments follow the introduction by Beijing last month of higher taxes on the export of certain resources and also a reduction in export quotas. The measures prompted the US and the European Union to file complaints with the World Trade Organisation. As the world's major commodities consumer, China relies heavily on imports of raw materials and the country has been scrambling to make overseas acquisitions to secure access to key resources in recent years. The latest bid by state mining group Chinalco to raise its stake in global mining giant Rio Tinto failed last month when Rio spurned the US$19.5 billion investment and chose instead to make a rights issue and establish an iron ore joint venture with rival BHP Billiton. Tensions escalated further last week when the government announced it had arrested Rio's Chinese-born Australian chief executive, Stern Hu, together with three deputies over allegations of espionage. Beijing responded to the WTO complaints from the US and the EU by saying the two countries were guilty of erecting their own unfair import barriers and also dumping their products on international markets. The Ministry of Commerce said its decision to impose export taxes and quotas on raw materials such as copper, bauxite, indium, yellow phosphorous, magnesium carbonate and molybdenum did not breach WTO rules and were aimed at protecting the country's precious resources. Following on the arrests of the Rio executives the government said it had 'sufficient evidence to prove they have stolen state secrets and have caused huge losses to China's economic interests'. Commenting last week on his calls for tighter trade restrictions, Mr Yang said: 'The US government also restricts its export of advance technology to other countries and halted production of some resources, including crude oil, uranium and rare earth. Why should China not do so?' China has the world's largest reserve of tungsten, indium and rare earth, and contributed more than 80 per cent of the world's output. Its production of molybdenum and germanium are also the largest in the world. Such metals are widely used in weapons manufacturing, aerospace, and the information industry. The US, which has the world's second largest reserves of rare earth, had halted exploitation of these resources since 1999, and was instead buying cheap raw materials from China and other countries, mainland media reported last week. China is the largest exporter of some rare metals and rare earth elements. From 1990 to 2005 its exports of rare earth increased nearly 10 times. But cutthroat competition for export among miners and over-exploitation had seen prices of such minerals plunge on world markets while depleting the country's reserves, said Mr Yang. Prices for rare metals and rare earth including indium and tungsten have fallen 30 to 40 per cent in the past five years and China's share of global reserves of rare earth dropped to 52 per cent last year, from 88 per cent a decade ago, while its global reserves of tungsten fell to 35.5 per cent from 45 per cent, according to data published in mainland media reports last week. Meanwhile, a report prepared by a research team under the Chinese Academy of Social Sciences' Institute of Industrial Economics, warned that Beijing's restriction on exports might undermine its validity to tap overseas resources.