Donald Trump tours Mexican border with Texas
Donald Trump has visited the Texas town of Laredo, on the US-Mexico border, vowing to tackle immigration.
Border security and immigration have been two key topics for Mr Trump since he announced his candidacy.
Mr Trump's blunt comments about Mexican immigrants have enraged Latinos across the country.
A local branch of border patrol agents who were going to host the Laredo event pulled out at the last minute. Mr Trump said they were "scared".
His team decided to go anyway "despite the great danger".
Mr Trump arrived wearing a hat with his campaign slogan "Make America Great Again".
The National Border Patrol Council Local 2455 said in a statement: "After careful consideration of all the factors involved in this event and communicating with members of the National Border Patrol Council at the National level, it has been decided... to pull out of all events involving Donald Trump."
Mr Trump's campaign said the group was "silenced directly from superiors in Washington who do not want people to know how bad it is on the border".
"They're afraid of saying what's happening. They were told 'silencio'. If I win, believe me, we'll get things straightened out," he added.
"Everybody wants me, they want the problem fixed, we have to have legal immigration," he said.
Mr Trump said former governor of Texas and fellow Republican presidential candidate Rick Perry did "a terrible job" with immigration.
He then said he employs "thousands" of Hispanic people who are "great people" who want legal immigration.
Asked if he would build a wall between Mexico and Texas, he said "We're going to look into building a wall, and the answer is going to be yes."
In Laredo, near the Mexican city of Nuevo Laredo across the border, more than 95% of the population is Hispanic.
Last month, Mr Trump called Mexican immigrants "rapists" and "criminals" after he announced his presidential run.
"The Mexican government is forcing their most unwanted people into the United States," he said.
At Thursday's event, he said Mexico is "booming" and "doing so well, beyond what anybody ever thought".
Mr Trump has spoken repeatedly about "dangers" along the US-Mexico border. He gave no clear answer when asked for evidence of specific danger.
Asked whether he would apologize to Mexican immigrants for his comments, he said they were "not offended" because the media misconstrued his remarks about them. He said he thought he would win the Hispanic vote.
Mayor Pete Saenz said it was a "pleasure" to host Mr Trump in Laredo.
"The excitement that he brings is also very on the plus side for our city."
"I'm a Republican, I'm a conservative, I'm in first place, I want to run as a Republican and I think I'll get the nomination," he said, dispelling previous comments made to The Hill newspaper that he may run as a third-party candidate because the Republican National Convention had not treated him properly.
"[Hillary Clinton] is easily the worst secretary of state in the history of the country. She's going to be beaten and I'm the one to beat her," he said.