President Donald Trump on Air Force One. REUTERS/Carlos Barria President Donald Trump on Sunday suggested that the blame for future terrorist attacks would lie at the feet of a judge who blocked his executive order temporarily barring immigrants from seven majority-Muslim countries from entering the US.

In a series of tweets, the president complained about Judge James Robart overturning the ban. His ruling was upheld Saturday by an appeals court in San Francisco.

"Just cannot believe a judge would put our country in such peril," Trump wrote. "If something happens blame him and court system. People pouring in. Bad!

"I have instructed Homeland Security to check people coming into our country VERY CAREFULLY," he continued. "The courts are making the job very difficult!"

The tweets were the latest in Trump's series of public barbs directed at the Seattle judge, who argued that the government did not effectively make its legal case for singling out the seven named countries. Robart was appointed by President George W. Bush.

Trump referred to him as a "so-called judge" on Saturday, predicting that the ruling would eventually be overturned by a higher court.

Though last week the administration attempted to minimize the number of travelers affected by the ban, Trump's tweets on Sunday claimed that the judge's order allowed unscreened travelers to pour into the US.

The Washington Post has estimated that about 90,000 people with visas to travel to the US would be affected by Trump's temporary travel ban, though The New York Times reported on Saturday that there did not appear to be a large uptick in travelers from the nations affected by the ban. The executive order signed by Trump also temporarily bars all refugees from entering the US and indefinitely bars Syrian refugees from entering the country.

Immigration experts contend that the US refugee application process — which requires US and UN background checks by multiple intelligence agencies and several in-person interviews that take up to two years — is one of the most difficult ways to enter the US.