President Donald Trump has ramped up his criticism of the US court system, accusing it of putting the country in peril.

His comments came hours after a federal appeals court rejected the Trump administration's request to reinstate a controversial ban on citizens of seven Muslim-majority countries from entering the US.

After an unusually long silence, Trump took to Twitter to say he could not "believe a judge would put our country in such peril", arguing that the court system was making it "very difficult" to secure the country.

Just cannot believe a judge would put our country in such peril. If something happens blame him and court system. People pouring in. Bad! — Donald J. Trump (@realDonaldTrump) February 5, 2017

Trump also said he had told US border officials to check arrivals "very carefully".

I have instructed Homeland Security to check people coming into our country VERY CAREFULLY. The courts are making the job very difficult! — Donald J. Trump (@realDonaldTrump) February 5, 2017

The ban, which also affected refugees, was blocked by federal judge James Robart on Friday.

The White House and two US states legally challenging the ban - Washington and Minnesota - have until Monday to present further evidence backing up their respective arguments.

Then, the court could schedule a hearing or rule on whether the ban should remain suspended.

In its appeal to Friday's freeze of the ban, the justice department said the suspension was causing "irreparable harm" to the American public.

It said Robart's ruling had run afoul of constitutional separation of powers, and "second-guesses the president's national security judgement".

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But the Ninth Circuit Court of Appeals rejected the government's request for the travel ban to be immediately reinstated, without offering a reason.

The restrictions on all refugees and travellers from Iran, Iraq, Libya, Somalia, Sudan, Syria, and Yemen went into effect on January 27, causing chaos at airports across the US and leaving travellers trying to reach the country in limbo. Refugees from Syria were blocked indefinitely.

The political backlash for Trump has been equally severe, with the order prompting numerous mass protests

Top technology giants, including Apple, Google and Microsoft banded together with nearly 100 companies on Sunday to file a legal brief opposing Trump's immigration ban, arguing that it "inflicts significant harm on American business".

Noting that "immigrants or their children founded more than 200 of the companies on the Fortune 500 list", the brief said Trump's order "represents a significant departure from the principles of fairness and predictability that have governed the immigration system of the United States for more than 50 years".

The controversial executive order also "inflicts significant harm on American business, innovation, and growth as a result," the brief added.

Trump, who during his campaign called for a temporary ban on Muslims entering the US, has repeatedly vowed to reinstate the ban.

'I'm ecstatic'

Over the weekend though, legal uncertainty over the ban allowed travellers from the targeted countries to travel to the US.

Fuad Shareef and his family were turned back while waiting to board in Baghdad as the travel ban initially came into force last weekend.

But when the ban was put on hold, they tried for a second time.

"The embassy contacted me and they said 'you are able to travel'," Fuad told Al Jazeera, after travelling with his family from Baghdad to Istanbul before passing safetly through immigration in New York.

Kamal Fadlalla, a 33-year-old Sudanese doctor, rejoiced upon his arrival to New York after spending a week stuck in his home country.

"It feels great," Fadlalla told AFP on Sunday at John F Kennedy International Airport. "It was a tough week actually."

Iranian graduate student Sara Yarjani, who was initially deported under Trump's order, arrived in Los Angeles.

"I am so grateful to all the lawyers and others that helped me," she said tearfully.

In Syria, a 25-year-old law graduate who asked not to be named said he was driving to Beirut on Sunday to catch a flight to Amman and then a connecting flight to New York.

"I jumped up and haven't been able to sleep since. I'm ecstatic," the man told AFP.

The state department has said visa holders from the seven countries are allowed to travel to the US as long as their documents have not been "physically cancelled".