United States authorities are following up on "urgent inquiries" from the Australian government on why Victorian Labor MP Khalil Eideh was stopped from boarding a flight into America.
The upper-house MP was on an official study tour travelling with fellow politicians when told he could not board the flight from Vancouver to Denver on Friday, despite having a valid visa organised through the Australian government.
Foreign Minister Julie Bishop promptly asked Australian authorities to step in.
"At the foreign minister's request, Australia's embassy in Washington made urgent inquiries of the US authorities as to what happened, and why Mr Eideh was refused entry to the United States last week," a spokeswoman for Ms Bishop told AAP on Tuesday.
"The US authorities are following up on our request for information."
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A spokesman from Mr Eideh's office on Tuesday said they would comment once the investigation was completed.
Mr Eideh, born in Lebanon to Syrian parents, had a visa for his US travels, and he said American authorities had not raised any issues during the application process.
"I've been discriminated against," Mr Eideh told reporters when he returned to Melbourne on Saturday.
"I'm very, very disappointed and frustrated."
The US Embassy referred questions on the ban to US Customs and Border Protection, which has not responded.
Mr Eideh signed a letter in 2002 professing loyalty to Syrian dictator Bashar Al-Assad while seeking to get the Syrian Honorary Consul in Melbourne removed.
But when the letter was made public in 2006, Mr Eideh said he had only added his signature to a letter penned by someone else, and he was loyal to Australia.
Mr Eideh has family in Syria and last visited the country over the Christmas break.
He doesn't believe US President Donald Trump's travel ban - which denies entry to America by citizens of Sudan, Somalia, Iran, Yemen, Syria and Libya - is behind his ban.
Victorian Premier Daniel Andrews said Mr Eideh had shown class in handling his "confronting" treatment.
