A one-time Islamic terrorist convicted of attempting to bomb a bus in Israel was granted US citizenship and has remained in the country for nearly a decade after federal officials uncovered his criminal history.

Court documents obtained by CNN have revealed how Vallmoe Shqaire managed to pass through the immigration vetting process without raising any red flags even after that process was bolstered post-9/11.

Shqaire was charged with illegally obtaining American citizenship by intentionally withholding his criminal record and past associations in September.

Those charges came almost ten years after he became a citizen in 2008, and eight years after federal authorities first learned about his bombing attempt.

Vallmoe Shqaire, 51, a one-time Islamic terrorist convicted of attempting to bomb a bus in Israel in 1988, was granted US citizenship in 2008 and has remained in the country for nearly a decade after federal officials learned of criminal record, court documents revealed (file photo)

Shqaire, who was born in Jordan, was trained by the Palestinian Liberation Organization in bomb-making and the use of rifles and grenades, the records filed in US District Court in Los Angeles indicate.

In 1988, Shqaire and an accomplice tried to blow up a bus 'on the direction' of a cell of the PLO, which was at the time considered a terrorist group by US officials.

The pair managed to detonate a pipe bomb within range of the vehicle, but no one was injured.

Shqaire, who went by the name Mahmad hadr Mahmad Shakir at the time, was convicted and sentenced to ten years in prison in 1991 but was ultimately released after four due to agreements under the Oslo peace accords.

He would later claim that he was coerced into confessing by members of the Israel Defense forces who beat him, subjected him to showers that were either scalding or freezing and confined him in a tiny dark cell for weeks.

Shqaire also accused Israeli authorities of repeatedly arresting his father to intimidate him, shooting his brother thinking it was him and evicting his family from their home before sealing it shut with cement.

US prosecutors concluded that 'such allegations are not supported by the certified court records Israel provided,' according to the filing.

Shqaire tried to blow up a bus in Israel 'on the direction' of the Palestinian Liberation Organization, which was considered a terrorist group by the US government at the time. PLO leader Yasser Arafat is seen speaking at a meeting of the Palestinian National Council in 1987

That conviction should have barred him from even entering the US, but he entered the country on a visitors visa in 1999 anyway.

He married a US citizen that same year to obtain a green card. The woman later told authorities that she met Shqaire on their wedding day and he paid her $500.

He didn't manage to get a green card through that marriage because they divorced in 2002. However, he got married a second time later that year and he was able to apply for and receive permanent residency.

On his application Shqaire indicated that he had never been arrested and was not a member of any group.

It was in November of 2008 that Shqaire's citizenship application was approved.

Court records indicate that he came onto the radar of US terrorism investigators two years later in 2010. His arrest and imprisonment for the bombing-related charge came to light that year.

During an interview with authorities, Shqaire acknowledged having been 'arrested and incarcerated in Israel on two different occasions', but he claimed that those arrests were for taking part in demonstrations, not terrorism.

'He stated that he was young and stupid at the time but was influenced by seeing innocent Palestinian men, women, and children injured or killed by Israelis,' court documents state.

'Shqaire claimed he would have never participated in events if he knew the consequences.'

He remained in the US throughout the drawn-out investigation, which uncovered fingerprint evidence conclusively linking him to the bombing in early 2016.

It is unclear why it took so long for the federal government to bring charges against Shqaire, who is currently out on bond and living in Los Angeles.

He reached a plea deal in January and is due to be sentenced on Friday.

'By concealing his violent, terrorist conduct, defendant circumvented the procedures our immigration system depends upon,' prosecutors wrote in a sentencing memorandum asking for Shqaire to be put behind bars for 16 months.

Shqaire was charged with illegally obtaining American citizenship by intentionally withholding his criminal record and past associations last September. His defense attorney, Mark Werksman (above), has asked a US district judge in Los Angeles to sentence him to probation at a hearing Friday, arguing that being expelled from the US is punishment enough

Shqaire's attorney, Mark Werksman, told CNN that the 51-year-old is not a threat to anyone.

'Mr Shqaire wanted nothing more than to be an American and to contribute positively to American society,' Werksman wrote in a sentencing memorandum.

The lawyer said that his client, who has worked as a parking valet for years, lied to US immigration officials so he could escape the Middle East for 'the comparative peace and freedom of life in America'.

Werksman is pushing for a sentence of probation, arguing that being expelled from the US is punishment enough.

He submitted several letters from Shqaire friends testifying that he is not the man he was years ago.

Werksman also said that this case is an embarrassment for the government, telling CNN: 'On paper, my client is a very bad guy. So, the question is: How did this happen?'

A US Citizenship and Immigration Services spokeswoman declined to discuss Shqaire's case because it is ongoing.

She told CNN that the agency's current leadership 'has enhanced the screening and vetting of those seeking immigration benefits to ensure they are eligible and do not pose a risk to national security'.

Shqaire is at least the second known convicted terrorist to slip through the immigration process since 9/11.

In 2017 Rasmieh Odeh pleaded guilty to illegally obtaining her US citizenship by not disclosing a 1970 conviction for her role in a pair of bombings in Israel, one of which killed two people.

Odeh was expelled from the country after having been a citizen since 2004.