Dorset County Hospital is struggling to hit its cuts target of £7.6m this financial year, according to a report.
The hospital in Dorchester needs to save 4.3% of its turnover but is yet to identify where £1.7m of the cuts will come from, the internal report says.
Governors will meet on Wednesday to discuss the figures, the Local Democracy Reporting Service said.
Documents show pay costs are already over budget, partly because of higher than planned nursing agency costs.
In her report to hospital governors, deputy finance director Rebecca King said: "The delivery of the savings target for the year remains very challenging with £1.7m of the target unidentified at the end of the quarter."
The report found, while pay is so far £172,000 more than planned, non-pay costs since April are down £192,000 due to "slippage" on programmes such as overseas recruiting.
At the last governors' meeting in May, trust chief executive Patricia Miller said nurses had already been recruited from Dubai to plug staff shortages.
In her latest CEO report, she said overseas recruitment and the newly-qualified nurse intake would "significantly narrow nursing gaps" and reduce agency costs.