EVERETT (Reuters) - Republican Donald Trump on Tuesday (Aug 30) night called Democrats the "party of slavery" and praised what he called the millions of African-Americans with career success, as he tries to revamp his outreach to minority voters.

Mr Trump has made much-maligned efforts to appeal to black and Hispanic voters, groups that generally support Democrats and are expected to vote heavily for rival Hillary Clinton in the Nov 8 election.

"The Republican Party is the party of Abraham Lincoln," Mr Trump said at a rally in Everett, Washington. "It is the Democratic Party that is the party of slavery, the party of Jim Crow and the party of opposition," he said, referring to racial segregation laws that once existed in the American South.

The Republican nominee has said Democrats failed minority voters with economic policies that have not improved their job prospects, but his attempts have been criticised for painting a bleak view of the lives of all black and Hispanic Americans.

Mrs Clinton last week released an ad mocking Mr Trump's attempts to reach those groups and showing headlines about a racial discrimination lawsuit the New York real estate mogul faced in the 1970s.

A prominent supporter of Mr Trump's apologised on Tuesday for sending out a tweet that showed a cartoon image of Mrs Clinton in blackface.

Mr Trump sought to correct course in Washington state on Tuesday, saying millions of black Americans "have succeeded greatly" in art, science, sports and other endeavours.

"But we must also talk about those who have been left behind, the millions suffering in disastrous conditions in so many of our inner cities," he said.

Mr Trump, who has made his criticism of a pending Pacific trade agreement central to his campaign, on Tuesday also visited a Seattle suburb home to a large Boeing Co plane manufacturing facility that depends heavily on Asian sales.

Mr Trump vowed at his rally that he would win Washington state, even though the state tends to support Democrats and that party's nominee, Mrs Clinton, leads by large margins in opinion polls ahead of the Nov 8 election.

The Republican nominee, however, presents a conundrum for the unions that represent workers at Boeing, the world's largest aerospace company.

He has courted manufacturing workers with vows to tear up trade agreements and scrap the 12-nation Trans-Pacific Partnership. "The destruction that Nafta started will be finished off if the Trans-Pacific Partnership is approved," Mr Trump said on Tuesday, referring to a separate deal with Canada and Mexico reached in the 1990s. He also has vowed to renegotiate that agreement.

Supporters of the Trans-Pacific Partnership (TPP) point to Boeing's aircraft sales to Asia to tout the benefits of the agreement. Secretary of State John Kerry visited a nearby plant earlier this year to rally support for the pact.

Manufacturing unions agree with Mr Trump on his opposition to TPP and the export of jobs overseas, but officials said they find his track record unconvincing.

"The fact is that Trump has had the opportunity to bring jobs to Americans, and he's chosen to outsource them," said Mr Larry Brown, legislative and political director for the International Association of Machinists and Aerospace Workers District Lodge 751, which represents about 32,000 workers in the state, mostly at Boeing.

Boeing produces some of its largest planes only miles from where Mr Trump spoke on Tuesday night. As they are assembled, the painted tails of the planes show the airlines that ordered them, and many are Asian. Major components of each plane come from overseas: South Korea, China and Europe.

Over the next 20 years, Boeing projects that Asian customers will account for 40 per cent of the total global jetliner's market, the company said in a recent report. "Trade is a huge part of the success of manufacturing in Washington," said Ms Linda Dempsey, vice-president of international economic affairs for the National Association of Manufacturers, which Boeing belongs to. "They are exporting $73 billion in manufactured goods."

But Mr Trump offers a more dire outlook, arguing that only he can keep Boeing from moving those high-paying manufacturing jobs from Washington to China. "They'll start taking your business away, and you won't have much of Boeing," Mr Trump told Seattle's Kiro radio on Monday.

Mr Trump has broken with the Republican Party's traditional embrace of free trade. He has vowed to rip up the TPP and renegotiate the North American Free Trade Agreement, or Nafta, the existing deal with Canada and Mexico which he blames for the loss of US jobs.

The Republican Party's support for free trade has put it in sync with large business groups such as the Chamber of Commerce and the National Association of Manufacturers.

Mr Tony Fratto, a former official in the administration of Republican George W. Bush, criticised Mr Trump as out of step with the party.

"Trump's policies in this area are really dumb generally, but are particularly dumb for a major exporting company," said Mr Fratto, who worked on behalf of a coalition of large companies, including Boeing, that were pushing for renewal of the Export-Import Bank.

Some voters in Washington state remain divided. Mr Kirk Hoeppner, 53, a business analyst at Boeing who lives in Granite Falls, Washington, said he will vote for Mr Trump and he agrees with his business views. But he was not sure closer ties to other countries would hurt jobs there. "Even if we ally with other countries, we're still going to sell more airplanes," Mr Hoeppner said.

Mr Corey McNally, 40, of Whidbey Island, Washington, has not decided whom he will vote for. "The union members love Hillary just because they're supposed to because she's a liberal," said Mr McNally.

And Mr Trump, whom he called "just kind of a big show", may be too late to change anything. "This company's been outsourcing jobs for years," he said of Boeing.