"We are crazy to allow them to operate in U.S. without tighter restrictions," the Senate Intelligence Committee member wrote.

In a tweet Monday morning, Rubio argued that the "problem with ZTE isn't jobs & trade, it's national security & espionage." He said telecom companies "can be forced to act as a tool of Chinese espionage."

The Florida Republican's criticism marks the first backlash to the president's effort from a notable lawmaker within his own party. Trump's reversal on ZTE, which he announced in a tweet Sunday, comes amid a high-stakes trade dispute between the world's two largest economies.

Sen. Marco Rubio on Monday criticized President Donald Trump 's pledge to help Chinese technology company ZTE , saying he hopes the president is not "backing down" from his hawkish stance on China.

Last month, the Trump administration barred U.S. companies from selling to ZTE, a telecommunications company, for seven years. The ban came in response to the firm shipping American goods to Iran and North Korea. It effectively crippled ZTE.

On Sunday, Trump said he and Chinese President Xi Jinping "are working together" to give ZTE "a way to get back into business, fast." "Too many jobs" were lost in China, the president added. He said he instructed the Commerce Department to "get it done."

Trump tweet: President Xi of China, and I, are working together to give massive Chinese phone company, ZTE, a way to get back into business, fast. Too many jobs in China lost. Commerce Department has been instructed to get it done!

In a subsequent tweet Monday afternoon, Trump made a vague reference to the ZTE action being "reflective of the larger trade deal we are negotiating with China and my personal relationship with President Xi." It is unclear what exactly the president meant.

Trump tweet: ZTE, the large Chinese phone company, buys a big percentage of individual parts from U.S. companies. This is also reflective of the larger trade deal we are negotiating with China and my personal relationship with President Xi.

Trump's tweet appeared to muddle comments made by his administration earlier in the day. On Monday, Commerce Secretary Wilbur Ross called ZTE an enforcement issue separate from trade policy. White House spokesman Raj Shah told reporters that Ross' comments reflect the U.S. government's view.

Shah said "this is part of a very complex relationship between the United States and China that involves economic issues, national security issues, and the like." He called it "an issue of high concern for China that's been raised with the U.S. government and with our administration at various levels."

Trump's shift on ZTE appears to be a concession as Chinese Vice Premier Liu He gets set to travel to Washington this week for trade talks. The U.S. and China have threatened one another with tariffs that could damage the American agricultural industry. Trump has repeatedly pledged to punish Beijing for alleged trade abuses and theft of U.S. intellectual property by Chinese companies.

In a separate tweet Monday morning, Rubio wrote that "I hope this isn't the beginning of backing down to China."

The U.S. and China are discussing a potential deal to relieve pressure on ZTE in exchange for Beijing pulling back tariffs on billions of dollars in agricultural products, Reuters and The Wall Street Journal reported.

Trump's pledge to help ZTE already sparked criticism on the Democratic side of Congress. In a statement Monday, Senate Minority Leader Chuck Schumer said Trump is "backing off" his tough actions against China and argued his policy would "make China great again."

House Intelligence Committee ranking member Rep. Adam Schiff, D-Calif., said Sunday that Trump "should care more about our national security than Chinese jobs."

Schiff tweet