US Vice President Kamala Harris says Democrats have got "some work to do." She held her first rally as the party's presumptive presidential nominee on Tuesday, in Milwaukee, Wisconsin, just days after former President Donald Trump accepted his party's nomination at the Republican National Convention in the same city.

Harris set out on the campaign trail two days after President Joe Biden announced he was stepping aside. She said her campaign is about two different visions for the nation, asking the rally-goers whether they "want to live in a country of freedom, compassion and rule of law" or one "of chaos, fear and hate."

Wisconsin is seen as a key swing state in November's presidential election. Trump won it by a narrow margin in 2016 before Biden captured it four years later.

Senate Majority Leader Chuck Schumer and House Minority Leader Hakeem Jeffries announced on Tuesday that they are endorsing Harris. They said the Democrats are "more united" than ever before and will keep their hold on the Senate and win back control of the House.

The party will confirm its nominee in an online "roll call" by August 7, and delegates will gather in Chicago for the Democratic National Convention in the middle of the month.