BOSTON (Reuters) - Japan has formally asked the United States to extradite a former Green Beret and his son accused of helping former Nissan Motor boss Carlos Ghosn flee the country while he was awaiting trial on financial charges.

Japan submitted a request to the US State Department to extradite Michael Taylor and his son, Peter Taylor, after they were provisionally arrested in Massachusetts in May, the US Justice Department said in a court filing on Thursday.

Lawyers for the Taylors did not immediately respond to requests for comment. Their lawyers have argued that they have not been charged in Japan with an offense for which extradition is possible under the US-Japan treaty.

The Japanese embassy in Washington and US Justice Department did not respond to requests for comment.

The Taylors were arrested in Harvard, Massachusetts, on May 20 at Japan's request after authorities there in January accused them of helping smuggle Ghosn, Nissan's former chairman, out of the country on Dec. 29, 2019, in a box.

Ghosn fled to Lebanon, his childhood home, after being charged with engaging in financial wrongdoing, including by understating his compensation in Nissan's financial statements. He denies wrongdoing.

Lebanon has no extradition treaty with Japan.

Both men have been held without bail since their arrest. Prosecutors have argued that neither Taylor, including Michael, a US Army Special Forces veteran and private security specialist, should be released from jail as they are flight risks.