Donald Trump has escalated his criticism of a federal judge who blocked a ban on travel from seven mainly Muslim countries, and said courts were making US border security more difficult, intensifying the first major legal battle of his presidency.

“Just cannot believe a judge would put our country in such peril,” Trump tweeted on Sunday, two days after James Robart suspended his restrictions on refugees and travel and a day after a panel of judges denied the White House’s emergency appeal to reinstate the ban.

The US president tweeted: “If something happens blame him and court system. People pouring in. Bad!”

The US has for years had some of the most rigorous vetting for visas and refugees in the world, and airlines have said travel has not yet recovered to levels that were normal before Trump’s order.

Trump’s tweets were the latest in his running attacks on courts. Earlier on Sunday, hid vice-president Mike Pence said Trump had “every right to criticize the other two branches of government” and was not “questioning the legitimacy of the judge”.

Trump added: “I have instructed Homeland Security to check people coming into our country VERY CAREFULLY. The courts are making the job very difficult!”

On Sunday morning, the president’s allies scrambled to his defence while his opponents hailed the courts as a barricade against a leader who Bernie Sanders said was moving the US “in a very authoritarian direction”.

Trump, who was spending the weekend at his Mar-a-Lago resort in Florida, had been unusually silent. The president had filled the week with morning tweets, sent like clockwork, defending his executive order to suspend travel from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen for 90 days, to halt the US refugee program for 120 days, and to shut down the Syrian refugee program indefinitely.

Signed nine days ago, the order caused chaos at airports around the US as officials detained and deported travelers who would have been allowed into the country only a day earlier, and protesters gathered.

Little more than a day after the order was signed, a federal judge in New York shut down a first provision, beginning the legal battle over whether Trump had violated the constitution’s limits on presidential power. On Friday Robart shut down the whole order temporarily.