Mairtin O Muilleoir has claimed there is "no possibility" that £55m in infrastructure cash will be lost to the Treasury because of the Brexit vote.
However, the Sinn Fein Finance Minister also admitted there were significant question marks" over how the Northern Ireland Investment Fund would now be operated.
The Belfast Telegraph revealed earlier this month that uncertainty over the future following the UK's decision to leave the EU meant that the European Investment Bank (EIB) was reassessing the means by which the money would be delivered.
There are also fears that any delay could lead to the cash being sent to Westminster if not spent by the end of the financial year.
But Mr O Muilleoir told the Belfast Telegraph: "First of all, there is no possibility of any of the funding that we had set aside going back to the Treasury."
He claimed the Treasury was "happy with how we are handling matter", but would not clarify the terms under which the £55m would not be returned to the Exchequer.
There remains uncertainty about how the money can be spent by the end of March, with proposed schemes having to work with the private sector.
Question marks also linger about how the Northern Ireland Investment Fund will be run, with the EU body meant to assist it all but pulling its support.
It was previously hoped the EIB would match the £55m and help the Executive secure a fund manager, as well as assisting in the delivery of the scheme.
Mr O Muilleoir said he and Economy Minister Simon Hamilton had written to the EIB to "continue discussions" over its involvement with the fund.
But he added that "at this time of uncertainty" and given how chilly relationships are with the EU, it was unlikely that the original model would go ahead, although the door "has not closed completely".
Mr O Muilleoir also admitted there were significant issues concerning how the fund would go forward. He claimed one option was to run it "off the balance sheet", with an independent investment body or fund in charge.
"We are in an area of negotiation and discussion," the Finance Minister added. "It is not going as exactly as promised."
However, Mr O Muilleoir also pledged that the money would not be lost and said he was committed to examining all options - including contacting investment funds - and ensuring there was an investment pot.
The intervention marks the first time the minister has spoken of his concerns for the future of the fund.
It comes after he came under intense pressure to urgently outline what he and his department intended to do to ensure that the money was not lost.
The department had advertised for a fund manager to operate the scheme, but the position is now on hold.
The programme was due to fund a range of infrastructure projects across Northern Ireland.
Among the areas meant to be targeted were urban renewal, telecoms and more.