NEW YORK (BLOOMBERG) - Michael Bloomberg said the "couple hundred million dollars" he's spent so far in his bid for the Democratic presidential nomination are an investment in preventing President Donald Trump from being re-elected in November, regardless of whether Bloomberg becomes the nominee.

"That's my investment in trying to get rid of Donald Trump and get us a decent president," Bloomberg said Tuesday (Jan 14) in a live appearance on CBS's "The Late Show with Stephen Colbert." The show aired immediately after the top six Democratic presidential candidates held their final debate before the Feb 3 Iowa caucuses.

The former New York mayor, who joined the presidential contest Nov 24, has already booked more than US$223 million (S$300 million) in advertising across the country, according to Advertising Analytics, which tracks political ads. The campaign also said Tuesday it has 1,000 staffers working in 33 states.

Even if he doesn't win the nomination, Bloomberg has pledged to keep "a chunk" of his staff working and major offices open to defeat Trump. Bloomberg did not rule out spending as much as US$1 billion if necessary, but said "hopefully not" that much. He said he would support Joe Biden, Bernie Sanders, Elizabeth Warren, Tom Steyer or "whoever's in the race." "Every single person on the stage today is better than Donald Trump," Bloomberg told Colbert.

Bloomberg also said while he doesn't agree with a wealth tax proposed by rivals Warren and Sanders, he would raise taxes on the wealthy.

"That's the way you fix income inequality, and that's where we get money to do the things that we need to do that keep this country safe and keep the economy going." Bloomberg is the founder and majority owner of Bloomberg LP, the parent company of Bloomberg News.

Bloomberg said he didn't interact much with Trump in New York when he was mayor but did play golf with him at a charity tournament once. Trump, he said, "has a reputation of not being, let's say, scrupulous in how he counts strokes."