Franklin Graham, who led prayer events in all 50 states last year in the run-up to the 2016 presidential election, is reiterating his warning about the dangers of Islam.
He's also urging people to pray that God would give wisdom to President Trump and others in Washington to deal with the threat.
"Since 9/11, I have been warning America about the dangers of the teachings of Islam," he wrote in a Facebook post. "Followers of Islam are taught very troubling passages that encourage them to murder and maim those they refer to [as] infidels, or nonbelievers."
He said that with the advent of the Internet and social media, "radicalization is only increasing – and the dangers are continuing to increase."
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"Many times, sadly, it is the young who are pulled into these teachings that encourage murder and rape in the name of the god of Islam," said Graham, who is president and CEO of  the Billy Graham Evangelistic Association and of the Samaritan's Purse relief and development ministry.
He cited the terrorist attacks in London on Saturday in which Muslim jihadists mowed down pedestrians with a van on London Bridge and then went on a stabbing spree in nearby pubs, killing at least seven and injuring 48.
The attacks were by "Muslim men who said this was for Allah," Graham said.
"That is three Islamic terror attacks in London in less than three months. The threat of Islam is real. The threat of Islam is serious. The threat of Islam is dangerous. There is cause for concern, despite what some may say," he said.
He urged his Facebook followers: "We need to pray that God would give our president, our Congress, and our Senate wisdom – and the guts to do what is right for our nation, and not what's politically correct. My prayer is that the United States – and the UK – will wake up before it's too late."
Last year, Graham criticized Pope Francis for claiming that while the world may be at war, the conflict has nothing to do with religion.
"It most certainly is a war of religion," Graham said.
CNN reported at the time Francis said the world "is at war because it has lost peace."
"There is a war of interest, there is a war for money, a war for natural resources, a war to dominate people. Some might think it is a war of religion. It is not," he said.
"All religions want peace. Others want war," the pope claimed.
Graham said: "I agree that the world is at war – but I disagree that it's not a war of religion. It is most certainly a war of religion."
He said religion "is behind the violence and jihad we're seeing in Europe, the Middle East, Asia, and here in this country."
"It's a religion that calls for the extermination of 'infidels' outside their faith, specifically Jews and Christians. It's a religion that calls on its soldiers to shout 'Allahu akbar' ["Allah is supreme" in Arabic] as they behead, rape, and murder in the name of Islam. Radical Islamists are following the teachings of the Quran," Graham wrote.
"We should call it what it is."
And only a few weeks earlier, Graham called out then-President Obama for refusing to acknowledge the threat from Islamic radicalism and terrorism after an Islamic terrorist attacked a "gay" bar in Orlando, killing 49 people.
Obama throughout his presidency refused to say the words Islamic terrorism or radical Islamic terrorism. Often, he insisted Islam is peaceful and those who carry out violence and terror against innocent victims in the name of Islam have "hijacked" the religion.
Graham, however, said that view obviously is wrong.
"I appreciate President Barack Obama speaking to the nation yesterday in the wake of the Orlando massacre. He was right in saying that this tragic shooting was an act of terror and hate," Graham wrote.
"But why didn't he say it was an act of radical Islamic terrorism?"
"Mr. President, with all due respect, don't forget Fort Hood; don't forget the Boston Marathon; don't forget San Bernardino; and don't forget 9/11. What do they all have in common? They were all Islamic terrorists carrying out their treachery in the name of their religion."
The non-partisan website the Religion of Peace has documented that 10 days into this year's Islamic Ramadan holiday, terror attacks in the name of Islam have numbered 55, with 592 fatalities.
"ALL other religions combined: 0 [and] 0," the site says.
Also, Muslims killed by "Islamophobes" total zero."
Since 9/11, "Islamic terrorists have carried out more than 30,954 deadly terror attacks," the site states, including 214 attacks with 1,552 homicides just during the month of May around the world.