WASHINGTON (Reuters) - The Air Force general picked by President Donald Trump to become the second-highest ranking U.S. military officer on Tuesday vehemently denied sexual assault allegations against him at his confirmation hearing, and received a strong endorsement from a senator who said she was raped while serving in the military.

“All of the allegations are completely false,” General John Hyten, nominated to become vice chairman of the military’s Joint Chiefs of Staff, said in dramatic testimony to the Senate Armed Services Committee, adding that “nothing happened, ever.”

His accuser, Army Colonel Kathryn Spletstoser, sat quietly in the room during the hearing, occasionally shaking her head in disagreement, and afterward told reporters that Hyten had lied to the senators under oath.

Hyten’s nomination has posed a challenge to the Senate, which for years has criticized the military for failing to do enough to combat sexual assault in its ranks. Lawmakers must now decide whether Spletstoser’s accusations should prevent Hyten’s confirmation by the Senate.

An official Air Force investigation did not substantiate the accusations against Hyten. Several lawmakers concluded after hearing from both Hyten and Spletstoser that the nominee had been falsely accused.

“The truth is that General Hyten is innocent of these charges,” said Republican Senator Martha McSally, the Air Force’s first female combat pilot.

“Sexual assault happens in the military. It just didn’t happen in this case,” added McSally, who this year said she had been raped by a superior officer while in the military.

Spletstoser has accused Hyten of engaging in unwanted kissing and touching as well as rubbing up against her.

“The bottom line is he lied about sexually assaulting me. He did it. He did it multiple times,” Spletstoser told reporters.

Spletstoser added that, were Hyten to be confirmed, it would send a message that victims “need not bother to report (sexual assault), they won’t be taken seriously.”

Trump, speaking to reporters at the White House following the hearing, said he was a fan of Hyten but that his confirmation was up to the Senate.

“We’re going to have to see how it all turns out,” said Trump, who in the past has denied allegations by a number of women who have accused him of sexual misconduct.

Heather Wilson, who served as Air Force secretary until stepping down this year, made a surprise appearance at the hearing, introducing Hyten by declaring he had been falsely accused.

FILE PHOTO: U.S. Air Force General John Hyten, Commander of U.S. Strategic Command, arrives to testify before a Senate Armed Services Committee hearing on Capitol Hill in Washington, U.S., April 4, 2017. REUTERS/Yuri Gripas/File Photo

Sexual assault and harassment in the U.S. military is largely under-reported and the official statistics show the problem is worsening. The Defense Department estimated in May that the number of sexual assaults climbed nearly 38 percent in 2018 compared with a survey two years earlier, data that critics have said laid bare broken Pentagon promises of a crackdown.

The Pentagon said there were 6,053 reports of sexual assaults last year, the highest since the U.S. military began collecting this kind of survey data in 2004.

‘SCOURGE ON OUR MILITARY’

Hyten said he would support reforms to address sexual assault within the armed forces, saying: “It is a scourge on our military.”

Democratic Senator Tammy Duckworth, a war veteran, appeared frustrated about the lack of specific recommendations by Hyten. Hyten said he was not a expert on the issue, which dominated his confirmation hearing.

Hyten is the outgoing commander of the U.S. military’s Strategic Command, which would oversee any nuclear conflict.

Republican Senator Joni Ernst, an Army veteran who said she was raped in college, raised concerns about Hyten’s response to complaints of Spletstoser’s “toxic leadership” while she was at Strategic Command. Specifically, Ernst said she was concerned that Hyten did not take sufficient action against Spletstoser until questions were raised about his own leadership.

“This leaves me with concerns about your judgment and ability to lead in one of the highest positions in the U.S. military,” Ernst said.

Still, many lawmakers rallied to defend Hyten.

Senator Jim Inhofe, the Republican chairman of the committee, criticized the news media for publishing details of Spletstoser’s accusations “with little regard for the truth.”

Inhofe said his committee had exhaustively looked into the allegations, holding five executive sessions, studying more than 1,000 pages of investigative records and reviewing statements from more than 50 witnesses.

“This committee takes allegations of sexual assault very seriously - it is unacceptable,” Inhofe said. “But this committee will not act on unproven allegations - allegations that do not withstand the close scrutiny of this committee’s process.”