President Obama on Tuesday blasted Republican presidential front-runner Donald TrumpDonald John TrumpIvanka Trump, Jared Kusher's lawyer threatens to sue Lincoln Project over Times Square billboards Facebook, Twitter CEOs to testify before Senate Judiciary Committee on Nov. 17 Sanders hits back at Trump's attack on 'socialized medicine' MORE for his plan to bar immigrants in the U.S. from sending money back home to force Mexico to pay for a new border wall.

"Oh, no. It's Trump," a smiling Obama said when he was asked about the 2016 candidate's latest comments.

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Obama called the plan another shortsighted idea from Trump that could spark concern among world leaders.

“I am getting questions constantly from foreign leaders about some of the wackier suggestions that are being made,” Obama told reporters at the White House.

Obama said Trump’s border wall proposal could have “enormous” economic consequences for Mexico, which receives billions of dollars in payments that immigrants in the U.S. send home, and possibly touch off a major spat with an ally.

“The notion that we are going to track every Western Union bit of money that’s being sent to Mexico — good luck with that,” Obama said. 

Obama's remarks came after The Washington Post published a two-page memo from Trump outlining how he would get Mexico to pay for his wall. Trump's memo outlines how he would cut off certain remittances — cash transfers from people in the United States to Mexico — unless Mexico's government offered $5 billion to $10 billion to pay for the wall. 

Mexican President Enrique Peña Nieto has said he won’t pay for Trump’s wall and claimed the candidate has damaged U.S.-Mexico relations. 
 
The country’s former president, Vicente Fox, slammed the proposal, saying, “I’m not going to pay for that f---ing wall.” 
 
World leaders are also asking Obama about Trump’s chief rival, Sen. Ted CruzRafael (Ted) Edward CruzSenate GOP to drop documentary series days before election hitting China, Democrats over coronavirus Democrats play defense, GOP goes on attack after Biden oil comments Quinnipiac poll finds Biden, Trump tied in Texas MORE (R-Texas), who has called to admit only Christian refugees from Syria and for special policing of Muslim neighborhoods, Obama said.

The president argued that both Trump's and Cruz’s ideas prove they are unfit to serve as commander in chief.

He called Trump’s remittance cut-off proposal “just one more example of something that’s not thought through” and made only for political purposes.

World leaders “don’t expect half-baked notions coming out of the White House. We can’t afford that.”

It's the third time in less than a week that Obama has taken aim at Trump's comments about foreign affairs.

He criticized Trump's proposal to allow Japan and South Korea to obtain nuclear weapons in comments at an international summit last Friday, calling it an example of the GOP front-runner's lack of foreign policy knowledge.

Obama also defended NATO as a "cornerstone" of U.S. and European security. Trump has called the Cold War-era alliance "obsolete" and said he would be happy to see it dissolve.

White House press secretary Josh Earnest said later Tuesday that he hasn't seen Trump's proposal, but he noted "it does sound consistent with the kinds of discriminatory policies and discriminatory rhetoric” that are a "hallmark" of the billionaire's stump speeches.

—This report was updated at 1:08 p.m.