Democratic Candidate Kamala Harris has picked Tim Walz as her running mate for the presidential election, US media has reported.

Walz, the Minnesota Governor and a former high school teacher, will become vice-president if Harris beats Donald Trump in November.

Harris interviewed several top contenders in Washington DC over the weekend and reportedly had not made up her mind until earlier today.

The announcement comes as Harris begins a tour of key battleground states, starting with a rally in Philadelphia later today where Harris will officially introduce Walz as her running mate.

Before being elected as Minnesota's governor in 2018, Walz was known as a battle-tested Democrat who served 12 years in Congress.

He has gained national attention for his strategy of calling Donald Trump and JD Vance "weird".

The phrase caught on with a number of Democrats - including Harris.

"He's just a strange, weird dude," Walz said of Trump during a fundraising event.

His plainspoken and small-town Midwestern persona could appeal to independent and conservative voters.

The 60-year-old led Minnesota through the 2020 protests over George Floyd's death in Minneapolis.

He deployed the National Guard to help quell riots that broke out during the demonstrations.

Mr Walz served more than 20 years in the Army National Guard, taught high school and also worked as an assistant football coach.

Minnesota is arguably less of a swing state, but would be a valuable asset for Harris. (BBC)