Hillary Clinton's overall favourable rating since clinching the nomination has averaged 41%, nearly matching her 40% in May but down slightly from 44% in January while Donald Trump's average 31% thus far in June compares with 32% in May and 34% in January.

WASHINGTON – Both US' presumptive presidential nominees Hillary Clinton and Donald Trump are gaining steam among their own parties, but remain unfavourable nationally, a poll issued on Monday found.

According to the poll conducted by research-based, global performance-management firm Gallup, since clinching the Democratic nomination earlier this month, Clinton's favourable rating among Democrats and Democratic-leaning independents has been up slightly to 71%, compared with 68% in April and May, Xinhua news agency reported.

At the same time, Trump's favourable rating among Republicans averaged to 64% in June, the same as in May but higher than the 54% to 56% in the three prior months, the poll found.

Despite steady or even sagging ratings nationally, Trump and Clinton have begun the process of repairing their images within their own parties as they prepare to officially receive their nominations at their respective conventions in July, it said.

While Clinton may have earned a bump from clinching the Democratic nomination, she has not built on that in the following weeks, perhaps because of her rival Vermont Senator Bernie Sanders' reluctance to withdraw from the race.

Trump, on the other hand, has picked up some additional steam among Republicans in June. It will be important to see if Trump can hold or build on his improved status among Republicans into July, the poll said.

Still, Clinton and Trump, who are the least favourable presidential candidates in decades, have each lost ground among independents who lean toward neither party.

Because of this, the candidates' national favourable ratings have stayed still or declined slightly, despite recent improved ratings from their own parties, it said.

Clinton's overall favourable rating since clinching the nomination has averaged 41%, nearly matching her 40% in May but down slightly from 44% in January.

Trump's average 31% thus far in June compares with 32% in May and 34% in January.