Republican Donald Trump on Monday said people with roots in Pakistan, Saudi Arabia and Somalia pose threats to the United States.Pointing to specific incidents such as the September 11, 2001, attacks, Trump said threats were posed by people with roots in Pakistan, Saudi Arabia and Somalia.Defending his immigration ban, he said it would last until "we are in a position to properly screen these people coming into our country. "They're pouring in, and we don't know what we're doing."Trump placed responsibility for a mass shooting in Florida squarely at the feet of radical Muslims, who he said were entering the country amidst a flood of refugees and "trying to take over our children."The presumptive Republican presidential nominee drew on the country's deadliest mass shooting to sharpen his vow to ban Muslim immigrants, proposing that the United States suspend immigration from areas of the world where there is "a proven history of terrorism." In his national security speech, Trump said it was time to "tell the truth about radical Islam," the day after 49 people were killed at a gay nightclub in Orlando by a gunman, likely self-radicalised, who had sworn allegiance to the rebel group Islamic State.His comments contrasted sharply to those of Hillary Clinton, the wealthy businessman's likely Democratic rival in the November 8 election, who urged increased intelligence gathering and more airstrikes on Islamic State territory, and cautioned against "demonising" American Muslims. "If we want to protect the quality of life for all Americans - women and children, gay and straight, Jews and Christians and all people - then we need to tell the truth about radical Islam and we need to do it now," Trump told the crowd in New Hampshire.He went on to lambaste Clinton's policies, saying they would allow "hundreds of thousands of refugees from the Middle East" to enter the United States without adequate security measures. There would be "no system to vet them, or to prevent the radicalisation of... their children," he said. "Not only their children, by the way. They're trying to take over our children and convince them how wonderful ISIS is and how wonderful Islam is, and we don't know what's happening."Trump said that, if elected, he would use the executive authority of the presidency to impose stronger controls on immigration to protect Americans from attacks, fine-tuning his earlier campaign promise to temporarily ban the entry of foreign Muslims to shore up national security.Trump's blunt comments come six months after he controversially called for a ban on Muslims entering the United States.He also expressed strong support for America's gay community, following Sunday's attack on the gay nightclub in Orlando left 50 people dead including the shooter."This is a very dark moment in America's history," Trump said."It's a strike at the heart and soul of who we are as a nation," he added."It's an assault on the ability of free people to live their lives, love who they want and express their identity."