Former US Vice-President Joe Biden is strongly signalling he could soon launch a presidential campaign while still giving himself room to decide against a run.

Speaking in Delaware, Biden said: "I haven't made the final decision but don't be surprised."

Biden says his family supports a campaign, which is important because he has long said that would be a major consideration for him.

He added, "There is a consensus that they ... want me to run."

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He says he's still deciding whether he can finance a campaign according to his principles, which include banning political action committee money.

He also says he would want to make sure he could run a first-class digital campaign that could position him to win the Democratic nomination.

-AP