HONG KONG/BEIJING (Reuters) - China's regulatory body for state assets said on Tuesday it would support central government-owned companies to increase their stock holdings and share buybacks to mitigate the impact of an escalating global trade war on the country's stock market.

Several Chinese state-owned companies, including oil giant Sinopec, have already announced plans to buy back shares to bolster investor confidence.

The government's assets supervision and administration commission will guide state-owned enterprises and their listed subsidiaries to safeguard the rights and interests of shareholders, and consolidate the market's confidence in listed companies, it said in a statement.

Last week, U.S. President Donald Trump introduced additional tariffs of 34% on Chinese goods as part of steep levies imposed on most U.S. trade partners, bringing the total duties on China this year to 54% and sending global stock markets tumbling.

The Chinese government has stepped up efforts to shield its economy from global market turmoil in response.

Trump has also threatened an additional 50% tariff on Chinese imports if China does not withdraw the 34% levies on U.S. goods it announced last week.

China's benchmark Shanghai Composite Index edged up on Tuesday, recovering some losses after plunging more than 7% the previous day.