WASHINGTON — A US woman with a history of making threatening phone calls to the United States Secret Service has been arrested and charged with threatening to kill First Lady Michelle Obama.

According to a criminal complaint obtained by AFP, Kristy Lee Roshia has been charged before a court in Hawaii with knowingly and willingly stating on November 10, 2009: "I will kill Michelle Obama."

Roshia has also been charged with assaulting a US Secret Service (USSS) agent who arrested her on December 19.

The affidavit attached to the criminal complaint says Roshia had traveled from the US mainland to Hawaii, where President Barack Obama and his family are scheduled to arrive shortly for a Christmas vacation.

On November 10, Roshia allegedly called the US Secret Service's Boston field office and threatened to kill Michelle Obama.

"Roshia once again stated that she 'will blow away Michelle Obama,'" the affidavit said, adding she even called the office back to add, "I'm extremely powerful and extremely dangerous."

Roshia reportedly has a history of making threatening calls to the USSS Boston office and agents interviewed her in 2004 after she left a message with the office stating she was an assassin.

She told the interviewing agents that "although her mission is to assassinate the president, she has no desire to hurt him," the document said.

Her calls continued and in 2007 began to increase in frequency to around five to ten telephone calls a day.

"Roshia's tone on the telephone continued to increase with rage, indignation and seriousness," USSS Special Agent John Woodruff wrote.

On December 19, two USSS agents, including Woodruff, visited Roshia in Hawaii, where she acknowledged having threatened Michelle Obama.

Roshia also claimed to to know exactly where the Obama family would be staying in Hawaii, though she told the agents she had traveled to Hawaii in September "to protect Obama."

The interview was sufficient to convince the agents to arrest Roshia, who also threatened to "blow away the whole Oval Office" as she was being taken into custody.

The Honolulu Advertiser reported Wednesday that a federal judge had ordered Roshia to undergo a mental competency examination and scheduled a next hearing for February 9.