BEIJING (REUTERS) - China will use all necessary means to defend the interests of the country and its companies against a U.S. trade investigation, a spokesman for the Ministry of Commerce said on Thursday (Aug 24).

The ministry on Monday expressed "strong dissatisfaction"with the US launch of the probe into China's alleged theft of U.S. intellectual property, calling it"irresponsible".

The probe is the Trump administration's first direct measure against Chinese trade practices, which the White House and US business groups say are bruising American industry.

"We will take all the necessary measures to resolutely defend the interests of China and Chinese firms" in the face of the unilateral U.S. actions, commerce ministry official Gao Feng told reporters at a regular news conference.

Gao also said that China's support for overseas investment by Chinese firms will not change, but that oversight of deals will increase and projects related to China's Belt and Road initiative will be given priority.

China's Cabinet released guidelines to manage overseas investments, with certain sectors encouraged and others restricted or banned outright. Mergers and acquisitions by Chinese companies in countries linked to the Belt and Road initiative have been growing at a rapid rate, even as the government takes aim at China's acquisitive conglomerates to restrict capital outflows.

"We will further improve the overseas investment reporting management system," said Gao, adding China would push forward legislation to govern foreign investment.