Mainland and Hong Kong stocks gave up earlier gains and ended lower on Tuesday as investors cautiously monitored US President Donald Trump's Asia tour, awaiting the meeting with his Chinese counterpart Xi Jinping and a potential deal to de-escalate trade tensions.

The benchmark Hang Seng Index was down 87 points, or 0.33 percent, at 26,346.

The Hang Seng China Enterprises Index lost 0.97 percent to end at 9,375 while the Hang Seng Tech Index shed 1.26 percent to close at 6,093.

Across the border, the benchmark Shanghai Composite Index was down 0.22 percent at 3,988, after earlier going past the key 4,000 points level for the first time since August 2015 to hit an intraday high of 4,010, while the Shenzhen Component Index closed 0.44 percent lower at 13,430.

The combined turnover of these two indexes stood at nearly 2.15 trillion yuan, down from 2.34 trillion yuan on Monday.

Shares related to military equipment and shipbuilding led gains while those related to precious metals suffered major losses, with a sub-index tracking the industry dropping 3.23 percent, tracking losses in gold prices in global markets.

The ChiNext Index, tracking China's Nasdaq-style board of growth enterprises, lost 0.15 percent to close at 3,229.

Gold prices extended losses on Tuesday to a near three-week low, ahead of global central bank policy announcements this week.

Investors are heading into Thursday's trade talks in South Korea between Chinese and US leaders with a sense of deja vu, excited by the proclamations of a truce and apprehensive that the real deal may offer far less to celebrate.

"The Trump-Xi meeting later this week may show further signs of de-escalation, but the pattern of 'escalate and de-escalate' will continue in the future," said Larry Hu, chief China economist at Macquarie.

"Both sides could walk back from the agreements, if something comes up in the future. Meanwhile, no competitive edge in trade war can last forever."

Innovation and technological self-reliance will remain Beijing's top priority in the next five years amid the US-China competition, Hu added.

The People's Bank of China will "maintain its supportive monetary policy stance and implement moderately loose monetary measures," governor Pan Gongsheng said on Monday, reaffirming the central bank's current policy stance.

The China Securities Regulatory Commission launched a new plan on Monday to streamline the qualified foreign investor regime, introducing measures to ease access requirements, improve operational efficiency and expand the investment scope. (Reuters/Xinhua)