Xi, in his phone conversation with Trump, urged calm.
It's unclear whether any actual repercussions for China, like sanctions or tariffs, would come from an investigation like this, and officials said there is no timeline for how long an investigation would take.
As the crisis has unfolded, Trump has alternated praising China for its help and chiding it for not ratcheting up pressure on its Asian neighbor.
On Tuesday, Trump said any additional threats from North Korea would be met with "fire and fury".
Yet analysts said the measure could also backfire, resulting in more hostility and tension between the world's two largest economies at a time when their cooperation is critical to a diplomatic resolution on North Korea. Trump tweeted Friday that military solutions are "locked and loaded, should North Korea act unwisely". They added that the trade measure would be carried out under the rules of worldwide law and would not trigger greater conflict with China.
When asked about the delay in the call on Saturday, the officials did not address the question directly.
He simply will initiate the latest investigation of intellectual property theft in a long line of them running back through past administrations.
As a prime example of what the officials called China's "unfair trade practices", they objected that the country requires American businesses that want to operate there to form joint ventures with state-run companies and share intellectual property with them.
In a background briefing with reporters on Saturday, White House officials pointed to frustration from USA businesses that they have to share intellectual property with China as a condition for doing business in the country.
"China is widely recognised as the biggest source of the problem", he said. Lighthizer will recommend whether an official investigation into trade practices is warranted. Meanwhile, 100 days of trade talks with the Chinese carried out in past months resulted in a few trade gains but not the ambitious changes the administration had hoped for.
Trump, in the past, has tied trade policy to national security.
Used frequently during the Reagan administration in the 1980s, the law allows the USA president to impose tariffs and other measures to force open export markets.
The investigation is being ordered under US Trade Act of 1974, which officials said permits the USTR to investigate acts, policies or practices of a foreign country to determine whether they are indeed unreasonable or discriminatory that burden or otherwise restrict US commerce. Trump made addressing the US trade deficit with China a centerpiece of his campaign previous year and has suggested raising tariffs on goods from China. That initiative sets forth a long-term plan for China's dominance in a wide variety of high-tech industries, including electric vehicles, advanced medial products and robotics.
The administration has been eyeing other moves to rebalance the U.S. "And I think China will do a lot more".