Trump later told reporters he would have various agencies, including potentially the Justice Department, "see if there's any truth to" Thiel's accusations.
Thiel has called on the FBI and CIA to probe Google on its relations with China, and alleged that the company worked with the Chinese military.
The top U.S. general, Marine General Joseph Dunford, chairman of the Joint Chiefs of Staff, expressed similar concerns about Google in a congressional hearing in March.
Google said in an email statement: "As we have said before, we do not work with the Chinese military."
At a wide-ranging U.S. Senate subcommittee hearing Tuesday about Google's content policies, the company's top government affairs official told Senator Josh Hawley, a Republican, that it did little business in China.
"Fundamentally in China we actually do very little today, certainly compared to any other major technology company," said Karan Bhatia, vice president for government affairs and public policy.
Bhatia rejected accusations that Google has been infiltrated by Chinese intelligence agents or that it has turned a "blind eye" to theft of its code. Its decisions about contracts with the U.S. government have not been based on pressure from China, he said.
He added that Google had "terminated" an effort to develop a search engine that abides by China's political censorship rules. Google would only launch such a service now in consultation with "key stakeholders," Bhatia said.
But under questioning from senators, Bhatia declined to commit to not censoring content in China or to undergoing a third-party audit of its content moderation policies.
The lack of commitment drew sharp criticism from Hawley.
"Clearly our trust and patience in your company and the behavior of your monopoly has run out," he said. "It’s time for some accountability."
Thiel has financially backed several Republican politicians at the state and federal level, including Trump and Hawley, who have expressed concern about the influence of Google's search and advertising businesses.
Thiel invested in Facebook Inc soon after its founding and is a director at the social media company, which is Google's top rival for online ad spending. He also is a director at data analytics software firm Palantir Technologies, which, like Google, competes to secure government technology contracts.
'HOURGLASS HAS RUN OUT'
Senators on Tuesday criticized Google over several issues, including whether it was biased against conservative content and why it has been slow to stop the spread of some graphic material.
Senator Richard Blumenthal, a Democrat, said Google's YouTube needed to do a better job of policing content.
"You can’t simply unleash the monster and say it’s too big to control," Blumenthal said. "The hourglass has run out."
Senator Ted Cruz, who chairs the Senate Judiciary panel which held the hearing, called Google "a black box" currently and said it must present more data to lawmakers about takedowns of conservative content versus liberal material. Such information could inform how to better regulate Google, he said.
Google's monopoly power and censorship "is a real threat to our democratic processes," Cruz said after the hearing.
Senator Mazie Hirono, the top Democrat on panel, described the "claims of anti-conservative bias" as baseless.
The hearing was a chance for Google "to be raked over the coals ... for common sense actions that are entirely within their rights," she said.
(Reporting by David Shepardson and Susan Heavey in Washington; additional reporting by Paresh Dave in San Francisco; editing by Jonathan Oatis, Tom Brown and Cynthia Osterman) ((+1-202-898-8300; Reuters Messaging: rm://firstname.lastname@example.org))