Donald Trump being interviewed in Japan at the G20 by Tucker Carlson

Donald Trump has hit out at Robert Mueller on Twitter and insisted the US military is “thrilled” to be taking part in his “Salute to America” celebration for the Fourth of July as the House Ways and Means Committee launches a lawsuit to acquire his tax returns.

In an exclusive interview with Tucker Carlson of Fox News broadcast on Monday night, the president criticised homelessness in American cities, spoke of his optimism that his trade war with China would ultimately be won and benefit farmers and accused the social media giants of “possibly illegally” blocking him from gaining new followers before expressing his desire to withdraw US troops from Afghanistan, which he called, “the Harvard of terrorists”.

A delegation of Democratic congressmen and women have meanwhile visited a number of migrant detention centres at the US-Mexico border in Texas, speaking out against the squalid conditions they found there and the behaviour of some Border Patrol agents overseeing the facilities.

Images released Tuesday by US government inspectors who visited facilities in South Texas where migrant adults and children who crossed the nearby border with Mexico are processed and detained showed overcrowding and seemingly unsanitary conditions.

As public outrage grows over the conditions in which thousands of people — some no more than a few months old — are being held by the US government, the report offered new cause for alarm.

It quotes one senior government manager as calling the situation “a ticking time bomb.”

“Specifically, when detainees observed us, they banged on the cell windows, shouted, pressed notes to the window with their time in custody, and gestured to evidence of their time in custody,” the report says.

BuzzFeed first reported on a draft version of the report, which blurs most faces in the photos.

An autopsy report also released Tuesday confirmed that a 2-year-old child who died in April had multiple intestinal and infectious respiratory diseases, including the flu.

Wilmer Josué Ramírez Vásquez is one of five children to die after being detained by border agents since late last year. Two of the other four also had the flu.