Terrorist threats made against the United States have forced officials to increase security at Patrick Air Force Base and the Cape Canaveral Air Force Station.

Threats made by Islamic State militants have forced threat levels at military bases to be raised to "Force Protection Bravo," which is the third highest threat level on the five-tier scale.

The third level of alert means the Cape Canaveral: Then & Now tour — the popular bus tour that takes guests from the Kennedy Space Center Visitor Complex into the Cape Canaveral Air Force Station — has been suspended, officials said Wednesday.

The tour takes guests to some of the historic launch pads at the Air Force station.

"Once security levels change, we look forward to returning to normal operations with the once-a-day tour into the Cape Canaveral Air Force Station," said Andrea Farmer, a spokeswoman for the Kennedy Space Center Visitor Complex, in an email.

Officials at the 45th Space Wing  said the heightened alert is in response to a generalized threat against the country.

Earlier this month, the Islamic State group claimed responsibility for a weekend attack at a center near Dallas, Texas, exhibiting cartoon depictions of the Prophet Muhammad.

The increased security will lead to delays at Cape Canaveral Air Force Station and Patrick Air Force Base, officials said.

It's unclear how long the heightened security level will be in place, but Farmer said the no other tours are impacted.

"The rest of our tours, including the KSC bus tour included in daily admission, remains operational as it goes only to Kennedy Space Center, not Cape Canaveral Air Force Station, which is under heightened security measures," Farmer said.