"Trump just failed his first foreign test. Diplomacy isn't as easy as it looks," said 68-year-old Clinton in a tweet.
Trump, 70, has almost no experience in foreign policy as compared to Clinton who served as the US Secretary of State during the first term of the Obama Administration.
Clinton's critical comment came after a controversy erupted on building a wall along the Mexico border, a major election plank of Trump.
However, Trump said that he never discussed this with the Mexican president.
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The Hillary Campaign slammed Trump for visiting Mexico to meet its president at his invitation.
"Donald Trump has made his outlandish policy of forcing Mexico to pay for his giant wall the centerpiece of his campaign. But at the first opportunity to make good on his offensive campaign promises, Trump choked," said John Podesta from Hillary for America Chair.
"What we saw today from a man who claims to be the ultimate 'deal maker' is that he doesn't have the courage to advocate for his campaign promises when he's not in front of a friendly crowd. We know who he is," he said.
However, the Trump campaign defended the decision to travel to Mexico.
"Today was the first part of the discussion and a relationship builder between Trump and President Pena Nieto. It was not a negotiation, and that would have been inappropriate. It is unsurprising that they hold two different views on this issue, and we look forward to continuing the conversation," said Jason Miller, senior communications advisor of the Trump campaign.
"Trump has boasted for months that he is going to get Mexico to pay for his ridiculous wall but when he came face to face with the Mexican President he got out maneuvered and then tried to cover it up on worldwide TV. Simply put, Donald got rolled," he said.
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