Donald Trump has offered Mike Pence the vice presidential spot on his Republican ticket, and Trump aides have told the Indiana governor the formal announcement event could be made on Saturday.

"I am pleased to announce that I have chosen Governor Mike Pence as my vice presidential running mate," Trump posted on Twitter, adding that he would host a news conference on Saturday at 11:00am (15:00 GMT).

The Republican presidential candidate had planned to announce his pick of running mate at a news conference on Friday morning, but postponed his announcement in the wake of the deadly attack in Nice, France.

Some US media had reported on Thursday that Pence would be chosen, but the Trump campaign had said no choice had been made, prompting speculation that the candidate had changed his mind.

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Pence, 57, has served as governor of Indiana since 2013 and also represented the state in Congress for more than a decade.

Trump has signalled that he wants an experienced politician to help his presidential ticket because he is a political outsider with no experience in governing.

Trump met Pence on Wednesday in Indiana, as he has done with other candidates he has said are his top choices. Trump himself had said that Pence was among his top picks, along with New Jersey Governor Chris Christie and former Speaker of the House Newt Gingrich.

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Pence is seen as a fiscal and social conservative who can appeal to a broad swath of voters in the centre-right party so that Trump can make himself more palatable to Republicans who have been wary of his candidacy.

Pence points to his work enacting the largest tax cut in state history and lowering business taxes, balancing the state's budget and efforts to draw businesses to the state. 

As governor, Pence came under fire after signing a so-called religious freedom bill that opponents said would have allowed businesses to discriminate against gays, but he later revised the legislation.

Pence, however, has disagreed prominently with Trump on a number of issues; he has spoken out against the Republican presidential candidate's controversial call for a ban on Muslims entering the US and on trade deals.

Pence had been in a tight re-election bid for governor and faced a Friday deadline to withdraw from that race in order to run for vice president instead.

Source: Agencies