WASHINGTON - US President Donald Trump said on Tuesday Mexico was "doing virtually nothing to stop illegal immigrants from coming to our southern border" and that he would soon give a response.

"Mexico's attitude is that people from other countries, including Mexico, should have the right to flow into the US and that US taxpayers should be responsible for the tremendous costs associated with illegal migration. Mexico is wrong and I will soon be giving a response!" Trump said on Twitter.

Trump, who is pushing ahead with building a wall along with parts of the US-Mexico border after failing to make Mexico pay for a barrier as he had promised during his 2016 election campaign, did not elaborate on his planned response.

The White House did not immediately respond to a request for comment on Trump's tweet, and whether he was referring to a request from Mexican President Andres Manuel Lopez Obrador for an agreement on development aid with the United States and other nations to address the flood of Central American migrants.

Lopez Obrador said on Monday that Trump had made a commitment for US investment in Central America and Mexico and had shown interest in his ideas, but that the next step was to sign an agreement.

Trump last month threatened to put tariffs on cars coming from Mexico into the United States if Mexico did not help Washington deal with the immigration and drug situation along the border.

The US government has said border officers apprehended nearly 99,000 people crossing the southern border into the country in April, the highest figure since 2007, as Trump administration officials decry what they call a humanitarian and security crisis.

Reuters