The Republic's bad bank is providing £15m in lending to complete a major office development close to the Waterfront Hall in Belfast.
The National Asset Management Agency (Nama) said the funding boost to Lanyon Plaza and The Soloist – both developed by William Ewart properties – was part of its plan to enhance the value of its assets in Northern Ireland.
Nama said work on the developments had been held up in recent years because of "market conditions".
Construction firm Patton had been fitting out the business before its administration in November last year, but H&J Martin has since taken over the work.
The agency has absorbed loans of £3.35bn on property in Northern Ireland.
International law firm Pinsent Masons has let some space in The Soloist to move in next year, while it's understood a Government agency has considered taking office space in Lanyon Plaza.
Nama chairman Frank Daly revealed the financing of the Lanyon Place buildings as he spoke to the Northern Ireland Assembly and Business Trust in Dublin yesterday.
Mr Daly said: "The agency is committed to providing more funding to debtors based in Northern Ireland in addition to the £123m we have already approved.
"We would urge debtors to share their proposals with us, as we want to fund projects that can deliver a strong commercial return."
The agency said it had approved £87m in sales in Northern Ireland since it was established in 2009.
Those sales include the Scottish Mutual Building in Donegall Square South, Belfast, which was recently sold for conversion into a hotel.
Finance Minister Sammy Wilson welcomed Nama's intervention. "Lanyon Plaza and the surrounding buildings including the Waterfront Hall are landmark buildings for Belfast city centre and the announcement will ensure that Lanyon Plaza will not now be lying idle."
Mr Daly said the project would create employment in companies during the building and fit-out and that the two buildings, if fully let, would have room for around 1,750 people.
David Wright, director at commercial property agents CBRE, welcomed the financing of the buildings.
"It will be great to see these two buildings being completed, and they will bring much needed good quality office space back onto the market."
The 90,000 sq ft Soloist Building was designed by world famous Norwegian architect Neils Torp. Construction work on phase one of the £17m property finished in 2010. Lanyon Plaza is a 100,000 sq ft, 15-storey office block with a fully-glazed facade which cost an estimated £45m. It also includes apartments, retail space and basement parking. Construction, which started in 2007, ground to a halt in 2010.