Amid a tough re-election battle, Sen. Pat Toomey, R-Pa., slammed Hillary Clinton as a bigger threat to the United States than Donald Trump.

Toomey however has yet to endorse the GOP nominee over Clinton.

"I've said Hillary Clinton is completely, permanently unacceptable. We have seen her in office. We have seen what she did. In addition to jeopardizing classified information that jeopardizes our security, we've seen the decisions that she has made," Toomey said Thursday on Philadelphia radio station WPTH's "Chris Stigall Show."

Toomey cited the Democratic nominee's failures in Libya and the Benghazi attacks, as well as "the incredible failed Russian reset."

"Point me in the direction of any place, anywhere in the world where our American interests are more safe and more secure today than they were when she became secretary of state. You can't. Because that place doesn't exist," he explained.

Toomey did make some critiques of Trump, who he has not yet endorsed.

"Look, I've got real problems with things that Donald Trump has said on foreign policy with regard to NATO, with regard to nuclear proliferation, but Hillary Clinton's got a track record of disastrous foreign policy," Toomey said.

Toomey's comments come a day after Sen. Mark Kirk, R-Ill., said despite his reversal of his endorsement of Trump, he will not vote for Clinton because of her support of the Iran deal.

On Monday, 50 GOP national security experts signed a letter warning about the repercussions a Trump presidency would have on the country's national security.

Toomey, the incumbent, is trailing Democratic challenger Katie McGinty by 3 points, according to a new poll released Thursday.