Billionaire businessman Michael Bloomberg is strongly considering entering the race for the US Democratic Party's presidential nomination.

The ex-New York City mayor is concerned the current field of candidates is not good enough to beat Donald Trump in the 2020 election, his spokesman says.

The 77-year-old is expected to file paperwork this week for the Democratic presidential primary in Alabama.

A total of 17 candidates are currently vying to take on President Trump.

Former Vice-President Joe Biden, Massachusetts Senator Elizabeth Warren and Vermont Senator Bernie Sanders are the Democratic frontrunners.

Some recent opinion polls have suggested that Ms Warren and Mr Sanders - who are regarded as to the left of Mr Biden - might lose against Republican Mr Trump if either won the party's nomination.

Mr Bloomberg's spokesman said: "We now need to finish the job and ensure that Trump is defeated. But Mike is increasingly concerned that the current field of candidates is not well positioned to do that."

So far this is only a single toe entering the water, but it's a significant one. The presence of the former New York mayor and multi-billionaire would set alight the race for the Democratic Party nomination.

The politician closest to Mr Bloomberg's centrist outlook is Joe Biden - but his campaign appears to be fading.

Mr Bloomberg has, I understand, been doing a lot of polling in early voting states like Iowa and New Hampshire.

This isn't the first time that he's eyed a run at the presidency, only to eventually decide against.

But in the past he's ruled himself out because he thought Americans wouldn't vote for a billionaire New York businessman. That concern no longer applies.

BBC