"Those who do not believe in our Constitution, or who support bigotry and hatred, will not be admitted for immigration into the country," Trump said. "Only those who we expect to flourish in our country — and to embrace a tolerant American society — should be issued immigrant visas."
Trump has called for a temporary ban on all Muslims coming to the United States, and said in recent weeks he plans to expand it. He did not specifically name countries or pinpoint religions in his speech, but forcefully said that people who have "hostile attitudes" toward the United States must be blocked from coming, as well as those "who believe that sharia law should supplant American law" or belong to or sympathize with terrorist organizations.
"Our new approach, which must be shared by both parties in America, by our allies overseas, and by our friends in the Middle East, must be to halt the spread of radical Islam," Trump said.
Trump said he would call for an international conference focused on doing that and would partner with King Abdullah of Jordan, President Abdel Fatah al-Sissi of Egypt and Israel.
He laid out a broad, nonspecific plan for destroying the Islamic State, including joint and coalition military operations, cutting off funding, and shutting off access to the Internet.
"Military, cyber and financial warfare will all be essential in dismantling Islamic terrorism," Trump said. "But we must use ideological warfare as well."
To do that, Trump said his presidential administration would oppose "oppression of women, gays and people of different faiths" and would be allies with, and amplify the voices of, "moderate Muslim reformers in the Middle East."
Trump sharply criticized the foreign policy of President Obama and Hillary Clinton when she was secretary of state, decrying it as "nation-building" and claiming it led the Islamic State to flourish around the world. Trump had falsely claimed last week that Obama was the "founder" of the Islamic State, something he initially repeated but later dismissed as sarcasm. Trump said Clinton doesn't have the judgment, temperament or "mental and physical stamina" to fight the Islamic State.
He ticked off a list of terrorist attacks that have taken place in the United States and Western Europe over the past year or so, and claimed that the world is now less safe than when Obama took office.
Trump said he believes the United States and Russia could find "common ground" in the fight against the Islamic State.
"They too have much at stake in the outcome in Syria, and have had their own battles with Islamic terrorism." Trump said.
Trump has praised Russian President Vladimir Putin and last month called on Russia to find and release thousands of emails from Clinton. (He later said it was a joke.) U.S. officials said there is strong evidence that Russia was involved in a hack of emails and voice mails at the Democratic National Committee.
On Monday, a Ukrainian official said more than $12 million in undisclosed payments were earmarked for Trump campaign manager Paul Manafort by the pro-Russian political party of Ukraine’s then-president, Viktor Yanukovych from 2007 to 2012. Manafort was a political consultant for Yanukovych at the time. He said Monday that he never received any off-the-books payment.
Trump made some false claims in his speech, including asserting that he was an “an opponent of the Iraq war from the beginning." In 2002, Howard Stern asked Trump if he supported invading Iraq.
“Yeah, I guess so,” Trump said.
Trump also said during his speech on Monday that President Obama “said he regards Libya as his worst mistake.” In a Fox News interview earlier this year, Obama was asked about his worst mistake in office.
“Probably failing to plan for the day after, what I think was the right thing to do, in intervening in Libya,” Obama said.
Trump has said if he is elected president the United States might rethink its role in NATO and suggested that his administration might not defend allies against a Russian attack if they didn’t pay their fair share to the alliance. Trump on Monday said the U.S. would work closely with NATO on fighting terrorism and suggested it created a new division to combat terror threats after he said the organization is obsolete; NATO has long worked on counter-terrorism.
Speaking in Scranton, Pa., shortly before Trump's speech, Clinton said Trump has no specific plan to dismantle the Islamic State.
“I’ve laid out my strategy for defeating ISIS,” Clinton said in Scranton, Pa. “We will strike their sanctuaries from the air,” and help local forces fighting on the ground, she said, and “surge” intelligence to try to prevent attacks in the planning stage. “We are making progress,” Clinton said.
“Donald Trump has been all over the place on ISIS. He’s talked about letting Syria become a free zone for ISIS. A major country in the Middle East that could launch attacks against us and others. He’s talked about sending ground troops — American ground troops. Well, that is off the table as far as I am concerned.”
The Republican nominee said that under his administration, the detention center at Guantanamo Bay would remain open, human intelligence would be highly valued and foreign combatants would be tried in military commissions. Immigration officers would be able to immediately deport people visiting the country who "preach hate" and those who immigrate to the United States would be expected to assimilate, he said.
"Assimilation is not an act of hostility, but an expression of compassion," Trump said. "Our system of government, and our American culture, is the best in the world and will produce the best outcomes for all who adopt it."
Anne Gearan in Scranton, Pa., contributed to this story.