US Republican presidential candidate Donald Trump has continued his appeal to black voters in the largely white state of Iowa, describing African-American citizens living in US inner cities as “trapped.”

However, Trump’s attempt to win African-American votes slipped up on Twitter where he was heavily criticised for appearing to insensitively use the shooting death of a prominent basketball player’s cousin for his political purposes.

In response to NBA player Dwyane Wade’s Tweet about his cousin, Trump wrote: “Dwyane Wade’s cousin was just shot and killed walking her baby in Chicago. Just what I have been saying. African-Americans will VOTE TRUMP!”

In Iowa Trump blamed what he said were the failed policies of the Democratic Party for causing the “crushing poverty” that blacks in urban neighbourhoods endure.

He also cited high murder rates, failing schools and high unemployment among black men in urban communities.

“We also have to talk about the many who are trapped [and] about the deplorable conditions in our inner cities,” he said. “As a father, as a builder, as an American, it offends my sense of right and wrong to see their conditions.”

The speech was a continuation of the Republican nominee’s recent attempt to reach out to African-Americans. Hillary Clinton, Trump’s Democratic rival in the race for the White House, holds a commanding lead in opinion polls that have surveyed blacks, who overwhelmingly vote for the Democrats.

In Iowa, Trump repeated a question he first asked last week – “What do you have to lose?” – which offended many middle class blacks for portraying their lives so negatively.

But on Saturday he also mentioned the millions of blacks “who have succeeded so greatly,” while focusing his message on those living in inner cities.

Dwyane Wade's cousin was just shot and killed walking her baby in Chicago. Just what I have been saying. African-Americans will VOTE TRUMP!

— Donald J. Trump (@realDonaldTrump) August 27, 2016

“To those suffering, I say vote for Donald Trump. I will fix it. It will get fixed,” he said. “And I add in all sincerity, what do you have to lose?”

Trump had been criticised for repeating the question before vastly white crowds in other states.

He also set off a firestorm during the week by describing Clinton as a “bigot” who only sees people of colour “as votes not as human beings worthy of a better future.”

Clinton countered by accusing Trump of building his campaign on “prejudice and paranoia.”

She also denounced Trump’s efforts to appeal to minority voters and released a campaign ad pointing to racial discrimination lawsuit filed against Trump in the 1970s.