BOAO, China (Kyodo) -- China's executive vice premier said Thursday his nation, the world's second-largest economy, resolutely opposes protectionism and is committed to safeguarding free trade as its trade war with the United States intensifies.

Ding Xuexiang, ranked No. 6 in the ruling Communist Party Politburo, also pledged China will further promote opening up and called on foreign companies to invest in the Asian country in his keynote speech at the Boao Forum for Asia.

"We should jointly safeguard the free trade system, uphold open regionalism and firmly oppose trade and investment protectionism," Ding told a ceremony at the four-day forum that runs through Friday. "No matter how the external environment changes, China will open wider to the world."

His remarks at the event on southern China's Hainan Island, billed as Asia's alternative to the World Economic Forum in Davos, Switzerland, came as the U.S. government of President Donald Trump imposed a series of punitive tariffs on China and other countries.

Despite challenges including the prolonged property sector crisis, Ding said China is confident of achieving its economic growth target for 2025 set at around 5 percent, stressing that Beijing "ranks among the world's fastest growing major economies and accounts for about 30 precent" of global growth.

The vice premier said China will "enforce more proactive and effective" macroeconomic policies, stimulating domestic demand, promoting the healthy development of the property sector and stock market, as well as preventing and defusing risks in key areas.

He also said Beijing will push forward innovation-driven, high-quality development centered on such areas as artificial intelligence, new energy vehicles and quantum technology.

"We warmly welcome businesses from all countries to invest and operate in China, joining the process of Chinese modernization and sharing China's development opportunities," he said.

Some 2,000 participants from about 60 countries and regions have attended the annual conference to discuss topics such as the implications of U.S. foreign policy on Asia, scientific and technological innovation, and cooperation with the Global South.

Lao Prime Minister Sonexay Siphandone and Nobel Peace Prize laureate Muhammad Yunus, chief adviser of an interim government in Bangladesh, are among the participants at the forum, which was first held in 2002.

At a panel discussion, former Chinese Vice Foreign Minister Zhou Wenzhong said Americans should be aware that Beijing has diversified its export market in recent years following the first round of a trade war with the United States under Trump, with destinations including the European Union and the 10-member Association of Southeast Asian Nations.

Jeffrey Sachs, an economics professor at Columbia University in the United States, also said the presence of the U.S. market has been declining as an export destination and the country is "not the source of China's growth anymore."

The professor recommended that China further expand its presence in other markets as "the world needs green and digital technologies," saying Beijing leads in fields such as renewable energy, electric vehicles and battery supply chains.