* Firtash criticises "unjust" action by United States
* Industrialist says arrest in Vienna politically motivated
* Firtash won't post 125 million euros bail Tuesday - court (Recasts with Firtash statement, adds bail delay, background)
By Michael Shields
VIENNA, March 18 (Reuters) - Ukrainian industrialist Dmytro Firtash, arrested in Austria last week at the request of the United States pending his possible extradition for suspected corruption, accused Washington on Tuesday of having him detained for "purely political" reasons.
Firtash, one of Ukraine's most influential oligarchs, thrived under ousted President Viktor Yanukovich and has close ties to Russia through his gas business, but U.S. and Austrian authorities deny his detention is linked to the current tense East-West standoff over Ukraine's breakaway region of Crimea.
The Austrian court holding him said Firtash, 46, had intended to post 125 million euros ($174 million) in bail on Tuesday - a record sum in Austria - but later said the funds had still not arrived, delaying his expected release from detention.
In his first public comments since Viennese police took him into custody on March 12, Firtash, who has interests in gas trading and chemicals, linked his detention directly to the crisis in Ukraine pitting the West against Russia.
"The reason for my detention in Vienna last week was without foundation and I believe strongly that the motivation was purely political," he said in a statement released through a Vienna public relations firm.
"The President of the United States of America, Barack Obama, has said that the United States will impose economic sanctions on Russia so as a Ukrainian, why I was detained is as bewildering as it was unfair," he said.
U.S. authorities have been investigating Firtash since 2006, Austrian authorities have said. Austria's Federal Crime Agency said last week Firtash was suspected of violating laws on bribery and of forming a criminal organisation in the course of foreign business deals.
"My detention will seriously threaten many Ukrainian jobs and destroy my business," Firtash said in his statement.
"But this unjust action by the United States cuts much deeper and, if their legal moves continue, further harm and anguish will be caused among my fellow Ukrainian citizens."
Firtash is not among 11 Ukrainians and Russians that Washington has targeted with visa bans and asset freezes in retaliation for Russia's annexation of Crimea. He is also not on a list of 21 officials approved on Monday by the European Union.
A spokeswoman for the Austrian court that ordered Firtash held last Friday for possible extradition to the United States said that, contrary to earlier expectations, he would not be released on bail on Tuesday.
"We don't have the money yet and I just got a call from the judge in charge that the money won't be wired today," she said. The spokeswoman gave no further details.
A source close to Firtash said he may now be held until Friday or next Monday but gave no reason for the delay.
A final decision on his extradition to the United States could take weeks. He has sworn not to leave Austria if he posts the record-high bail, which the court said took into account his wealth and the gravity of the allegations against him.
The U.S. government will ask Austria to extradite him to face charges filed in a Chicago court, U.S. prosecutors said on Friday.
Firtash's Group DF company has called the case a "misunderstanding" that should be resolved soon.
Firtash, who has hired the law firm of former Austrian justice minister Dieter Boehmdorfer to represent him, has appealed against the court order that he be kept in detention.
The industrialist could also appeal against the court's final extradition ruling and he could take the case to Austria's justice ministry if an appellate court were to rule against him.
Forbes Ukraine magazine last year put Firtash in 14th place on its Ukrainian rich list, setting his fortune at $673 million.
Earlier on Tuesday, defying the Western sanctions and Ukrainian protests, Russian President Vladimir Putin signed a treaty making Crimea part of Russia.
($1 = 0.7180 Euros) (Editing by Gareth Jones)