President Donald Trump on Saturday announced he was relaxing the ban on US companies selling to the Chinese tech giant Huawei.

The announcement alarmed some US lawmakers including Sen. Marco Rubio, who said it would be a "catastrophic mistake" to loosen restrictions on Huawei.

Larry Kudlow, the director of the National Economic Council, said this new exemption would apply only to selling "general merchandise" to Huawei.

The Commerce Department in May had barred US firms from selling hardware or services to Huawei without receiving government permission.

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President Donald Trump has drawn fire after announcing plans to relax the ban on US companies doing business with the Chinese tech giant Huawei.

At the G20 summit in Osaka, Japan, on Saturday, Trump told the press he would allow US companies to continue to sell to Huawei, despite having placed Huawei on a trade blacklist in May over national security concerns. The Commerce Department ban meant no US business could sell parts and components to Huawei without a special license, though many firms reportedly skirted the ban.

Read more: Wall Street was ready for the latest twist in the trade war. Here's how experts think Trump and Xi's trade truce will play out.

In a later tweet, Trump said he'd reached the decision following pressure from US "High Tech companies" and Chinese President Xi Jinping. The Financial Times reported last month that Google was furiously lobbying Washington to keep doing business with the company.

Sen. Marco Rubio of Florida was quick to respond, tweeting that loosening the restrictions on Huawei would constitute a "catastrophic mistake."

"If President Trump has in fact bargained away the recent restrictions on #Huawei, then we will have to get those restrictions put back in place through legislation," Rubio added.

The administration's top economic adviser, Larry Kudlow, the director of the National Economic Council, downplayed Trump's relaxing of the ban, saying in an interview with CBS on Sunday that it applied only to "general merchandise," which he described as "various chips and software and other services that are available all around the world, not specific to the US."

"The president is not backing off on the national security concerns — we understand the huge risks regarding Huawei," Kudlow said, adding that talks with China over Huawei were ongoing. "The last word is not going to come till the very end of the talks."

Asked specifically about Rubio's criticisms, Kudlow said: "I hope that when President Trump comes back, that he and others of us will be able to persuade Senator Rubio that there will be no national security violations."