US President Donald Trump on Thursday lashed out at a campaign rally at Democratic opponents like “crazy Nancy” Pelosi, speaker of the US House of Representatives, for pushing an impeachment inquiry.

“The more America achieves, the more hateful and enraged these crazy Democrats become. They’re crazy. They’re crazy,” Trump said at a packed American Airlines Center in downtown Dallas.

Pelosi accused Trump of having a “meltdown” after walking out of a White House meeting on Wednesday where she and other Democratic leaders complained about his decision to pull US troops from northeastern Syria and allow Turkey to attack America’s Kurdish allies in the area.

“Crazy Nancy. That Crazy Nancy, she is crazy,” Trump said of Pelosi.

Trump has faced a backlash from his own Republican allies in Congress for the Syria pullout but he said on Thursday a ceasefire negotiated by Vice President Mike Pence with Turkish President Tayyip Erdogan had helped ease the crisis.

He told the Dallas crowd his approach was “unconventional” but he believed it worked. The death toll from Turkey’s week-long incursion into northeastern Syria was unclear.

“Without spilling a drop of American blood, not one drop of American blood, we’ve all agreed on a pause, or a ceasefire, in the border region of Syria,” Trump said. “Sometimes you have to let ’em fight for a while. Then people realise how tough it is.”

Pelosi opened an impeachment inquiry in the House on revelations that Trump pressed Ukrainian President Volodymyr Zelenskiy to investigate unsubstantiated allegations against former Vice President Joe Biden, a leading Democratic presidential contender, and his son Hunter Biden, who was on the board of a Ukrainian gas company.

Trump dismissed the impeachment inquiry as a “witch hunt” and said Democrats are trying to overturn the results of the 2016 election that he won.

Trump’s appearance in Dallas was aimed at rallying his core base of voter support in a state that he is favored to win in the November 2020 presidential election.

Texas has not voted for a Democratic presidential candidate since Jimmy Carter in 1976 but an increase in Democratic voters in big cities like Austin and Houston could make it a closer race in 2020 than it has been in the past.

Trump would not be expected to be re-elected should he lose the state’s 38 electoral votes.

Trump was concluding a long day in Texas in which he raised $5.5 million for his re-election campaign and the Republican National Committee at two events.