MELBOURNE (Reuters) -Fortescue reported a slump in first-half profit on Thursday, missing analysts' forecasts, and said it was reconsidering the timeframes for some of its green energy projects given policy uncertainty from the Trump administration.

Australia's iron ore majors, including bigger rivals Rio Tinto and BHP reporting this week, have seen profits narrow to pre-COVID-era lows as prices for the steelmaking ingredient came under pressure from slowing Chinese demand, particularly in the property sector.

Fortescue, the world's fourth-largest iron ore miner, said underlying attributable net profit after tax fell 53% to $1.55 billion for the six months ended December 31, amid falling prices of iron ore and higher costs.

That missed a Visible Alpha consensus estimate of $1.76 billion. Fortescue also declared an interim dividend of A$0.50 per share, which was 7% lower than the consensus, sending its shares down 7.5% compared to smaller losses in other major miners.

"Given revenue was in line... the result is attributed to higher costs," Macquarie said in a note. Revenue for the first half was $7.6 billion, matching consensus estimates while unit costs rose by 8% to $19.17 a tonne due to inflationary pressures.

The miner also revised its full-year forecast for its green energy unit's capital expenditure to $400 million from its previously provided forecast of $500 million.

"Market conditions are uncertain, with the Trump administration instructing federal agencies to pause grant payments under the Inflation Reduction Act," the company said about its green energy projects.

In July last year, the miner said the unit, Fortescue Energy, was unlikely to meet its target of producing 15 million metric tons of green hydrogen by 2030.

Green iron is produced by reducing iron ore using hydrogen gas, which is then converted into steel in an electric arc furnace.

"Market will want to see energy capex (capital expenditure) and opex (operating expenditure) cut further," analysts at Citi said in a note.

Fortescue is reconsidering the development timeframes of its U.S. Arizona project and the Gladstone hydrogen project in Australia.

The company said it had put under review the timeline for its Iron Bridge magnetite facility to get to capacity of 22 million tonnes a year but that it was on track to achieve the fiscal 2025 target for shipments of 5.0 to 9.0 million metric tonnes.

(Reporting by Melanie Burton in Sydney, and Roshan Thomas and Sherin Sunny in Bengaluru; Editing by Anil D'Silva and Muralikumar Anantharaman)