US President Donald Trump’s re-election campaign has raised $US10 million ($12 million) in the first quarter of the 2018, leaving his re-election operation with $US28 million ($35 million) in cash.

President Trump spent $US3.9 million ($5 million) in the first quarter.

Mr Trump has opted – unlike presidents before him – to begin actively fundraising in the early part of his first term. He could use some of the money which he has already raised to help Republicans in the upcoming midterm election in November.

In addition to raising money for his own campaign, Mr Trump has also collected funds for joint efforts with the Republican National Committee, which uses that money to help congressional candidates.

His re-election campaign finished 2017 with $US22 million ($28 million) in cash.

Mr Trump’s campaign has used millions of his campaign cash in the past year to pay legal fees – including some fees associated with responding to the Russia investigation being conducted by Special Counsel Robert Mueller. His campaign spent over $US3 million ($3.8 million) in 2017 in legal fees.

During the first quarter of the year, Mr Trump spent about $US834,000 ($1 million) on legal expenses – down from the $US1.1 million ($1.4 million) he spent in each of the previous two quarters, according to disclosures filed with Federal Election Commission.

In addition to legal fees, he has also used that money to keep a small campaign staff, to fund campaign rallies and to pay for digital advertising focused on his supporters.

Mr Trump filed for re-election the day he took office, an unusual move for an incumbent president.

Traditionally, incumbent presidents have waited until after their second year in office to begin their re-election campaign.

Mr Trump will stand for re-election in November 2020.

-AAP