WASHINGTON (AFP) - US President Donald Trump, fresh from a political holiday in Paris, went back on the offensive Sunday as a new poll showed his popularity dropping amid doubts about Russian election meddling and deepening frustrations over stalled health-care legislation.

In a tweet early Sunday, Trump used some of his toughest language against a favoured target, the press, saying: "With all of its phony unnamed sources & highly slanted & even fraudulent reporting, #Fake News is DISTORTING DEMOCRACY in our country!"

Trump also sent one of his private lawyers, Jay Sekulow, onto five Sunday talk shows to argue that there was nothing illegal about son Donald Trump Jr's meeting last year with a Russian attorney following a promise of damaging information on Democratic rival Hillary Clinton.

"What took place at the meeting...is not a violation of any law, statute or code," Sekulow told NBC. He repeated an earlier assertion that Trump is not the subject of any current investigation into alleged Russian efforts to tilt last year's election in the Republican's favour.

The concerted pushback came as a Washington Post-ABC News poll near the six-month point in Trump's administration showed him facing significantly declining approval ratings, down from 42 per cent in April to 36 per cent.

Similarly, the president's disapproval rating has jumped five points to 58 per cent, according to the survey of 1,001 adults.

Trump responded to the survey in a tweet, saying: "The ABC/Washington Post Poll, even though almost 40% is not bad at this time, was just about the most inaccurate poll around election time!"

Nearly half of respondents - 48 per cent - said they "disapprove strongly" of the president's performance in office, a low level never reached by ex-presidents Bill Clinton or Barack Obama, both Democrats, and reached only once by George W Bush, during his second term.

And 48 per cent said they saw American global leadership weakening since Trump entered the White House, while 27 per cent said it is stronger.

That would seem to show mixed results, at best, from a series of high-profile foreign visits by Trump, including to Saudi Arabia and to a Group of 20 meeting in Germany, where he met with Russian President Vladimir Putin. Trump's Bastille Day visit to Paris came a day after the poll ended.

Two-thirds of respondents said they do not trust Trump, or trust him only somewhat, in negotiating with foreign leaders.

Republicans' legislative struggles may also be weighing on Trump's popularity. Twice as many of those surveyed preferred the Obamacare health programme as favored Republican plans to replace it.

The US Senate will "defer" its work on repealing Obamacare for a week as senior lawmaker John McCain recovers from blood-clot surgery, the chamber's Republican leader, Mitch McConnell, said Saturday. The repeal effort is opposed by all Democrats, and the loss of a single Republican vote could doom it.

Trump had seemed to revel in his brief Parisian respite from all the talk of Russia and health care. He and President Emmanuel Macron reviewed a pomp-filled Bastille Day military parade and dined in a posh restaurant on the Eiffel Tower.

The US president then spent two days playing maitre d' to professional female golfers taking part in a tournament at his Bedminster course in New Jersey. Wearing his signature red "Make America Great Again" hat, the president waved to cheering onlookers Sunday as he entered a glass-enclosed viewing booth.

Trump was due to fly back to Washington in the evening.

But his return brings him straight back into the intensifying storm over his campaign's contacts with Russia.

Even some erstwhile supporters seem to be troubled by the Russia contacts of Trump's son and advisers, and by the administration's shifting explanations.

Shepard Smith, an anchor on Fox, a network that has often been in lock-step with the Trump White House, accused the administration of "mind-boggling deception". He added, "If there's nothing there, and that's what they tell us, why all these lies?" And key Democrats, like Mark Warner, vice chair of the Senate intelligence committee investigating Russian meddling, have expressed deep skepticism over administration attempts to gloss over the Trump Jr meeting.

News of the meeting was "very troubling", said Warner. "Clearly this administration has not been forthcoming." He told a CBS interviewer he wanted to hear from everyone who attended the meeting - which would include Trump son-in-law Jared Kushner and former campaign head Paul Manafort - adding that the recent revelation "obviously moves our whole investigation to another level."