Democratic presidential candidate Beto O'Rourke declared that immigrants make the country safer as he staged rallies across Texas on Saturday to formally kick off his 2020 White House bid, looking to shore up his deeply conservative home state and champion the US-Mexico border at a time when President Donald Trump has threatened to shut it.

The former congressman, who represented El Paso for three House terms until last year, began the day addressing 1,000-plus supporters in his hometown, across the border from Ciudad Juarez, Mexico. He later spoke at the historically black Texas Southern University in Houston, before finishing with a late-night Austin event, addressing a large crowd a stone's throw from the pink-granite state Capitol.

Bounding onto a makeshift El Paso stage in a blue-button-down shirt to The Clash's "Clampdown," Mr O'Rourke declared: "We are safe, not despite the fact that we are a city of immigrants and asylum seekers. We are safe because we are a city of immigrants and asylum seekers."

"We have learned not to fear our differences, but to respect and embrace them," he told a crowd that waved small American flags and black-and-white signs reading "Viva Beto" while often interrupting their candidate to chant his first name. Mr O'Rourke also spoke at length in his native Spanish, eliciting loud and sustained cheers.

In a series of tweets on Friday, Mr Trump warned he could close the US southern border next week "if Mexico doesn't immediately stop ALL illegal immigration coming into the United States." In later comments to reporters he added: "We'll keep it closed for a long time. I'm not playing games."

Who could be running against Trump in 2020? Show all 23 1 /23 Who could be running against Trump in 2020? Who could be running against Trump in 2020? Joe Biden The former vice president - poised to be a frontrunner - has announced his run. He recently faced scrutiny for inappropriate touching of women, but was thought to deal with the criticism well AFP/Getty Who could be running against Trump in 2020? Bernie Sanders The 2016 runner-up has announced that he will be running again in 2020 Getty Who could be running against Trump in 2020? Hillary Clinton The 2016 Democratic presidential candidate and former Secretary of State says she is “still considering” whether she will run again. Getty Who could be running against Trump in 2020? Pete Buttigieg The Indiana mayor and war veteran will be running for president. If elected, he would be the first openly LGBT+ president in American history. Getty Who could be running against Trump in 2020? Kamala Harris The former California attorney general will be running for president in 2020. Introduced to the national stage during Jeff Sessions’ testimony, she has endorsed Medicare-for-all and proposed a major tax-credit for the middle class. AP Who could be running against Trump in 2020? Elizabeth Warren The Massachusetts Senator has formally launched her bid for president in 2020. A progressive Democrat, she is a major supporter of regulating Wall Street. AP Who could be running against Trump in 2020? Beto O’Rourke The former Texas congressman told Oprah Winfrey that he “has been thinking about running for presidency”, but stopped short of formally announcing his bid to run in 2020. AFP/Getty Who could be running against Trump in 2020? Wayne Messam Mayor of the city of Miramar in the Miami metropolitan area, Wayne Messam has announced his bid. He intends to run on a progressive platform against the "broken" federal government. He favours gun regulations and was a signatory to a letter from some 400 mayors condemning President Trump's withdrawal from the Paris Climate Accord. Vice News Who could be running against Trump in 2020? Kirsten Gillibrand The New York Senator formally announced her presidential bid in January, saying that “healthcare should be a right, not a privilege.” Getty Who could be running against Trump in 2020? Cory Booker The New Jersey Senator has announced that he will be running for the presidency in 2020. If he secures the nomination he said finding a female vice president would be a priority. Getty Who could be running against Trump in 2020? John Delaney The Maryland congressman was the first to launch his bid for presidency, making the announcement in 2017. AP Who could be running against Trump in 2020? Julian Castro The former San Antonio mayor announced his candidacy in January and said that his running has a “special meaning” for the Latino community in the US. Getty Who could be running against Trump in 2020? Tulsi Gabbard The Hawaii congresswoman announced her candidacy in January, but is likely to face tough questions on her past comments on LGBT+ rights and her stance on Syrian President Bashar al-Assad. Getty Who could be running against Trump in 2020? Andrew Yang The entrepreneur has announced his presidential candidacy, and has pledged that he would introduce a universal basic income of $1,000 a month to every American over the age of 18. AFP/Getty Who could be running against Trump in 2020? Marianne Williamson The author and spiritual advisor has announced her intention to run for president. She had previously run for congress as an independent in 2014 but was unsuccessful. Getty Who could be running against Trump in 2020? John Kerry The former secretary of state has said he is still thinking about whether to run. Getty Who could be running against Trump in 2020? Michael Bloomberg The entrepreneur and former New York mayor– with a net worth of around $50bn – has said he will decide by the end of February whether to seek the presidency. AFP Who could be running against Trump in 2020? Howard Schultz Former Starbucks CEO Howard Schultz has not yet ruled out running for president in 2020, despite criticism that his bid could help re-elect Mr Trump by dividing the Democrat vote. AP Who could be running against Trump in 2020? Eric Holder The former attorney general has said he will decide in “the next month or so” whether to run as a 2020 presidential candidate. AP Who could be running against Trump in 2020? Eric Swalwell The California congressman said he is “ready to do this” and will decide before April whether to run. MSNBC Who could be running against Trump in 2020? Terry McAuliffe The former Virginia governor, who worked to elect Democratic governors during 2018 midterms, said there was a “50 per cent” chance he would run. AP Who could be running against Trump in 2020? Sherrod Brown The Ohio senator is still undecided about whether to run for president in 2020. Who could be running against Trump in 2020? Mitch Landrieu The former New Orleans mayor said he doesn’t think he will run for president, but “never say never”. AP Photo/Jacquelyn Martin

Mr O'Rourke has made promoting the border as culturally rich and economically powerful the centrepiece of his campaign and spoke on a downtown street corner a few blocks from it. He decried federal officials' recent decisions to hold people who crossed into the US to seek asylum "in cages" under El Paso's international bridge, saying those detainees "are our fellow human beings and deserve to be treated as our fellow human beings."

Mr O'Rourke entered the race 14 March and has already visited nine states, but had promised to return to El Paso for an official kick-off.

As he has previously, he renewed calls to work with Republicans and Democrats, saying "before anything else, we are Americans first" and prompting chants of "USA! USA!" But he also made bolder predictions than in the past, saying that if his campaign can bring people from across the ideological spectrum together he can top the rest of the crowded Democratic 2020 presidential field and "defeat Donald Trump."

A small but vocal group of El Paso Trump supporters had other ideas, gathering a few blocks away from the event to shout anti-O'Rourke sentiments for hours.

Mr O'Rourke represented the city in Congress for six years, but gave up his seat while nearly upsetting Texas Republican senator Ted Cruz in November. The Democrat who replaced him in the House, representative Veronica Escobar, welcomed those on hand to the "beautiful, magical, safe and secure US-Mexico border," adding, "When the border sends America her people, we are sending them our best in Beto O'Rourke."

Amy O'Rourke, who has largely avoided the spotlight since her husband began running for president, gave a short speech too, telling the crowd, "Listening to people is what gives Beto strength. It fuels him and it gives him context (with) which he can think about policies and the things he wants to do for this great country."

Despite such nods to bipartisanism, however, Mr O'Rourke offered many positions on Saturday that were liberal enough to make moderates nervous. He vowed to legalise marijuana nationally, defend abortion rights, sign new sweeping voting rights legislation to end partisan gerrymandering and allow automatic and same-day voter registration, institute federally financed, universal pre-kindergarten programmes, strengthen unions and bring home all troops from the US-led wars in Iraq and Afghanistan.

He also renewed his support for a House proposal called "Medicare for America," which he says will guarantee universal health care coverage while allowing people who like getting insurance through their employer to continue doing so.

'Walls do not save lives, walls end lives', says Beto O'Rourke at El Paso rally

Mr O'Rourke hit many of the same points hours later in Houston, but recalled a school shooting near that city last year to advocate for nationwide federal background checks on firearms purchases. He added that assault weapons "sold to the United States military with the sole purpose of killing people as effectively, as efficiently and in as great a number as possible" should be "kept on the battlefield" and not "sold into our communities.”

Addressing thousands and wearing a Texas Southern baseball cap, Mr O'Rourke also recalled the devastation in Houston of 2017's Hurricane Harvey, saying the US must do more to combat climate change and that the nation's fourth-largest city understands the phenomenon's dangers "better than just about anyone in this country."

Concluding in Austin, he called that city's liberal politics "the centre and the source of so much of what is good for Texas and for the United States of America."

Texas has not elected a Democrat to statewide office in 25 years. But Mr O'Rourke came within 3 percentage points of beating Mr Cruz, and his party is hoping that a booming Hispanic population and large numbers of new residents moving in from other states could keep Texas close in 2020 — potentially reshaping the electoral college. California senator Kamala Harris drew a large crowd last weekend when she too visited Texas Southern.

"This state and its 38 electoral votes count like they've never counted before," Mr O'Rourke said in El Paso. "All of us matter."