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Mexican President Enrique Pena Nieto said Thursday that Republican standard-bearer Donald Trump's proposals represent a "threat" to his country, a day after the two men met in the Mexican capital.

Pena Nieto has been widely criticized in his country for inviting and meeting with Trump, as well as for not confronting him more directly about comments calling immigrants from Mexico criminals, drug-runners and "rapists," and Trump's vows to build a border wall and force Mexico to pay for it.

Speaking at a town hall where he fielded questions from young people, Pena Nieto sought to defend his decision. He said the easier path would have been to "cross my arms" and do nothing in response to Trump's "affronts, insults and humiliations," but he believed it necessary to open a dialogue to stress the importance of the U.S.-Mexico relationship.

He acknowledged Mexicans' "enormous indignation" over Trump's presence in the country and repeated that he told him in person Mexico would in no way pay for the proposed border wall.

The president came under fire for not responding to Trump's mention of the wall during a joint news conference Wednesday, something he has since sought to correct. Earlier Thursday, after Trump tweeted that Mexico would pay for the wall, Pena Nieto fired back his own tweet saying that would "never" happen.

Pena Nieto also rejected a recent investigative report that found large portions of his law thesis 25 years ago were copied from other sources, although he allowed that some authors were "probably" not cited properly.

"I remember very clearly the studies I carried out, what I researched and what I formulated in my thesis. Nobody can tell me I plagiarized my thesis," the president said. "I may have committed some methodological error, but not with the aim of wanting to make someone else's ideas mine."

Aristegui Noticias' report about the thesis last month was the latest bad news in what analysts say has been a very tough year for Pena Nieto. An Aug. 11 poll by the newspaper Reforma put his approval rating at about 23 percent, lower than for any Mexican president since it began conducting the survey 21 years ago.

Homicides are on the rise after falling early in his term. The economy has been struggling due to low oil prices and other factors. The Treasury Department recently lowered Mexico's GDP growth forecast yet again to between 2 percent and 2.6 percent.

There have also been allegations of torture and human rights abuses by police and troops prosecuting Mexico's offensive against the drug cartels, and earlier this year a group of independent experts issued a scathing report discrediting government investigators' account of what happened to 43 students who disappeared in 2014 after being taken by state police.

Pena Nieto appeared at the town hall hours after sending his annual state-of-the-nation report to congress. In the report and in a video broadcast before he took questions, he mostly tried to put forth a rosier vision for Mexico.

Pena Nieto praised things such as the use of technology to fight organized crime, several transportation projects, growth in auto manufacturing and a new national anti-corruption system. He said 62 million Mexicans now have access to the internet, 21 million more than when he took office in 2012. Officials have now proctored 700,000 evaluation exams for active and aspiring teachers under an education reform that he passed and which continues to inspire unruly protests by dissident teachers.

Pena Nieto also highlighted five areas Mexico needs to prioritize going forward: education, poverty, security, corruption and helping families.

"In various regions crime continues to be a threat. Corruption and impunity hurt the life of the country, and economic growth is still insufficient," the president continued. "This is what afflicts and affects Mexicans. They are serious problems that must be resolved."

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Peter Orsi on Twitter: www.twitter.com/Peter_Orsi