United States President Donald Trump has threatened to remove millions of peoplewho entered the country illegally "as fast as they come in."Trump wrote on Twitter that the U.S. Immigration and Customs Enforcementnext week will "begin the process of removing the millions of illegal alienswho have illicitly found their way into the United States."The series of comments come as Trump preparesto officially start his re-election campaign Tuesday night.Limiting immigration was a central issue of Trump's 2016 campaign.And he is expected to use the same issue in the upcoming 2020 campaign.The president also suggested that he will soon sign an agreement on migration with Guatemala.The agreement would make Guatemala the country where migrantsfleeing El Salvador and Honduras would go to seek asylum instead of the U.S. or Mexico.Trump said the Central American country would become part of effortsto limit migration in the area with a tweet on Monday:"...Guatemala is getting ready to sign a Safe-Third Agreement," he wrote.A U.S. State Department delegation traveled to Guatemala last weekto seek approval for the "safe third country" policy.If it is signed into law, it might be the first agreement of its kindbetween the U.S. and a Latin American country.However, Guatemala has not made a public statementthat it is ready to complete the deal.In the same Tweet, Trump praised Mexico for its effort to deal with migration at its borders:"...Mexico, using their strong immigration laws,is doing a very good job of stopping peoplelong before they get to our Southern Border," he wrote.Meanwhile, the U.S. State Department had announced plansto freeze some aid money to El Salvador, Guatemala and Honduras.State Department spokesperson Morgan Ortagus said aid already targetedfor the three so-called "Northern Triangle" countries would be provided.However, she said new money would not be provided until the administration is satisfiedthat these governments are taking clear measures to reduce migration to the U.S. border.Some American lawmakers have urged that the administration not cut aid.They are worried that doing so would make the migration problem worse.The Northern Triangle countries face high crime ratesand weak economies within their borders.Veronica Escobar represents the border city of El Paso, Texas,in the U.S. House of Representatives.She said, "Instead of working with leaders in Central America to stabilize the situation there,the administration is eliminating aidintended to create better conditions that would help keep families home."The human rights group called The Washington Office on Latin America,also disagreed with the decision to freeze some aid.The group said: "Cutting all aid to Central America is not the way to build a safer,more prosperous region where people aren't forced to flee."In March, the Trump administration said it would cut aid to El Salvador, Guatemala and Honduras.It noted the president's unhappiness with the three countries' immigration policies.Ortagus said that the State Department's decision came after a study of current policies.She said that aid in the form of grants and contractsthat had been provided for earlier would continue at current levels.Aid supporting justice and security issues would also continue, Ortagus said.