United States President Donald Trump on Tuesday declared “a humanitarian crisis – a crisis of the heart and a crisis of the soul” as he demanded funding for a wall along the Mexico border.

Trump cited instances where undocumented immigrants allegedly committed crimes against US citizens, including the rape of an Air Force veteran and the murder of a policeman of Indian origin. “How much more American blood must we shed before Congress does its job?” he asked.

In his first televised address to the nation from the Oval Office, Trump argued for funding on security and humanitarian grounds and urged the Democrats to return to the White House to meet with him, saying it was “immoral” for “politicians to do nothing”.

“This is a choice between right and wrong, justice and injustice,” Trump said. “This is about whether we fulfil our sacred duty to the American citizens we serve.”

He said: “Some have suggested a barrier is immoral. Then why do wealthy politicians build walls, fences, and gates around their homes? They don’t build walls because they hate the people on the outside, but because they love the people on the inside. The only thing that is immoral is the politicians to do nothing and continue to allow more innocent people to be so horribly victimised.”

Trump mentioned Ronil Singh, a police officer of Indian origin who was killed allegedly by an undocumented immigrant in California in December, and described him as a national “hero”. “America’s heart broke the day after Christmas when a young police officer in California was savagely murdered in cold blood by an illegal alien,” the US president said. “The life of an American hero was stolen by someone who had no right to be in our country.”

Trump had on Sunday held firm on his demand for funding from the Congress for the wall and had threatened to declare a national emergency to secure the money. Constructing the border wall was one of Trump’s main electoral agenda in the 2016 presidential elections.

The House of Representatives, which is controlled by the Democratic Party, has refused to allocate the $5 billion sought by the Trump administration, resulting in a partial government shutdown that has paralysed the US government for almost three weeks. Last week, the House passed legislative measures to reopen the government. But Trump threatened to veto it and the Republican-controlled Senate also decided not to approve the measures.