WASHINGTON — US President Donald Trump brushed aside concerns about a Democratic wave in this year’s congressional elections, telling Republican lawmakers on Tuesday there is "no reason" they cannot win.

With his party’s control of Congress hanging in the balance, Trump warned against "complacency" and bragged that his administration’s agenda "is already exceeding our highest expectations."

There is "no reason whatsoever" Republicans won’t win, Trump said, touting his economic record. "In this election we are fighting to win and we are going to win."

Privately, Republicans are less optimistic, spooked by a series of special election losses in traditionally Republican districts and states.

Trump’s approval ratings remain low after a chaotic first year in office and polls show Democrats almost ten percentage points ahead in a ballot considering only party preference and not specific candidates.

Republicans cannot afford to lose any more seats in the Senate, where they hold 51 of 100 seats, and control of the House of Representatives appears under serious threat.

But Trump has surprised before, not least in 2016 when he won the Republican presidential nomination and went on to shock the world by taking the White House.

"We are going to defy the predictions once again. We will keep the House majority," Trump said.

Republicans in the House currently have 238 seats to 193 for the Democrats, with four vacant.

Opening a new line of attack ahead of the general elections in November, Trump painted Democrats as a party of radicals that are "destroying the American dream."

There is no such thing as a conservative Democrat, "they are all Pelosi Democrats" he said, pointing to Nancy Pelosi, the Democratic leader in the House of Representatives, who has become a hated figure for the right.

"They are going so far to the left-hand side of the equation" he said, "we have to go a little bit further right."

If Democrats win control of the House of Representatives, he warned, "they will block every single effort to secure our borders."

That may be just the beginning of Trump’s concerns, as a Democratic House could reinstate investigations into his conduct and even begin impeachment proceedings. — AFP