U.S. President Donald Trump is meeting with Republican lawmakers Tuesday about immigration legislation amid growing cries for him to end his migrant policy separating children from their parents at the U.S. southern border with Mexico as they illegally enter the United States.Trump, in several Twitter comments, continued to defend his break-up-the-families policy, saying, "We must always arrest people coming into our Country illegally." He said, "Now is the best opportunity ever for Congress to change the ridiculous and obsolete laws on immigration. Get it done, always keeping in mind that we must have strong border security." The House of Representatives is set to vote later in the week on two immigration bills, including provisions that would curb the separation of children from their parents at the border. The measures would also create a path to citizenship for up to 1.8 million young immigrants already in the U.S. who were brought illegally to the U.S. years ago by their parents, but it is not clear that either piece of legislation has enough votes to win passage.In a meeting with Republican senators Monday, Trump threatened to shut the government in late September, as a new fiscal year starts October 1, if Congress does not approve $25 billion in funding for a wall along the Mexican border to thwart further illegal migration into the U.S. So far, Congress has approved little funding for the barrier, keeping Trump from meeting one of his signature vows during the 2016 presidential campaign. Numerous Republican and Democratic lawmakers have called for Trump to abandon the border policy as indefensible. All four former living U.S. first ladies, Michelle Obama, Laura Bush, Hillary Clinton and Rosalynn Carter, condemned the separation of children from their parents.Trump's wife, Melania Trump, through a spokeswoman, said she "hates to see children separated from their families" and that the U.S. should be "a country that follows all laws, but also a country that governs with heart."One Republican governor, Maryland's Larry Hogan, in an act of protest of Trump's policy on breaking up families when they are detained, withdrew the state's small National Guard contingent from the border where it had been assisting federal agents. Another Republican governor, Massachusetts' Charlie Baker, dropped his offer to send troops to the border.In a Washington speech, Trump said Mexico does "nothing for us" to block the flow of immigrants from reaching the U.S."If you don’t have Borders, you don’t have a Country!" Trump tweeted. He once again inaccurately blamed opposition Democrats for the border dispute, even though his administration set the policy on separating children from their parents."Democrats are the problem," Trump tweeted. "They don’t care about crime and want illegal immigrants, no matter how bad they may be, to pour into and infest our Country, like MS-13. They can’t win on their terrible policies, so they view them as potential voters! Mexico weighed in on the controversy, strongly rebuking Trump."In the name of the Mexican government and people, I want to express our most categorical and energetic condemnation of this cruel and inhuman policy," Foreign Minister Luis Videgaray told a news conference.