Evangelist Franklin Graham has warned that the United States "cannot afford to let our guard down" amid the threat of radical Islam and urged President Obama to acknowledge that "the enemy is here".

"It's confirmed - San Bernardino shooter Syed Rizwan Farook was a devout Muslim. Friends say he had memorized the Quran. The headlines say Farook and his wife were a couple 'bent on jihad,'" Graham said of the couple who massacred 14 people and injured 21 others at a holiday party at the Inland Regional Center in San Bernardino, California last week.

The 64-year-old evangelist expressed disbelief that President Barack Obama and his administration continue to blame the attack on gun control when "it was caused by hate-filled hearts intent on killing infidels in the name of Islam."

"Take away the guns and this couple would've still slaughtered innocent civilians," he continued. "Their apartment was a bomb-making factory! It's happened in France and it's happening here. ISIS has warned us that more attacks like this are going to follow. Next time it could be a mall or a school, but until our politicians understand and admit the threat of radical Islam we're going to have more of these horrible acts of violence."

As reported by the Gospel Herald Farook's wife, Tafsheen Malik had pledged allegiance to the ISIS chief Abu Bakr Baghdadi before the massacre, but was allowed into America on a "K-1" fiancé visa.

"Mr. President, we don't need more gun control - we need border patrol," Graham emphasized. "No Muslims should be allowed into this country until there's a process in place to fully vet them. We've got to turn away those who could potentially pose a threat until this war with radical Islam is over."

Within hours of the shooting, a team from Billy Graham Rapid Response Team traveled to San Bernardino to provide emotional and spiritual care to the traumatized city, according to a news release from the Billy Graham Rapid Response Team (BGRRT).

"We are encouraging churches to open their doors to address the needs of the community," said Jack Munday, international director of the Rapid Response Team. "One of the biggest questions right now is, 'How can a loving God let this happen?'"

In a separate Facebook post shared a short time later, Graham asked fellow Christians to continue to pray for the family members of the shooting victims and said he is praying that America's leaders will make the right decisions concerning radical Islam.

"Let's pray for the families of these American men and women who were gunned down senselessly by an Islamic couple committed to terrorism in the worst terrorist attack in this country since 9/11," he wrote. "We cannot afford to let our guard down. The enemy is here."