Representatives of the Union of Fans - an umbrella group comprising six different organisations - held talks with King in Glasgow yesterday.
And they will meet with the South Africa-based businessman once again in a few days to complete the details of the scheme.
The Union and King both want the club board to provide security over Ibrox and the training ground at Auchenhowie before they release funds to them this summer.
The former director, who once invested £20million of his personal fortune in his boyhood heroes, is set to meet with the board during his visit to Scotland.
A Union of Fans statement read: "There is now a firm commitment from all parties to move forward.
"More details of the set-up of the trust, trustees and how fans can take part will be released in the coming days.
"It is our intention to ensure that fans have full transparency of how the trust will work and we will keep them updated on a regular basis.
"It is clear from today's meeting that Dave King shares the concerns of supporters with regard to the desperate need for investment in the club.
"He has indicated that he is willing to provide that investment by taking a lead role in a fan-based initiative and we are fully supportive of the terms on which he wishes to do so.
"We have arranged to meet again early next week to move the plans forward once he has completed a series of further meetings over the weekend.
"We would hope to then be in a position to release specific details."
Meanwhile, over 30,000 blue leaflets will be distributed to fans attending the SPFL League One game against Dunfermline at Ibrox this afternoon.
Fans are being asked to hold them up in the 18th and 72nd minutes of the match to highlight their support of King.
Elsewhere, Ally McCoist has admitted extending their run in the Scottish Cup this season could make a huge difference to the financial situation at Rangers.
He said: "I think that would affect our budget. If we can get through the replay against Albion Rovers on Monday it sets us up for a great home semi-final against Dundee United.
"After last Sunday there are no givens. But I wasn't aware just how much it's worth, but it it's over £1million. That's a lot of money to our club and any club for that matter."
Meanwhile, McCoist has revealed Andy Little and David Templeton, who limped off in the win over Airdrie in midweek, may be out of action long term.
He also he confirmed Lewis Macleod,who has been out with a virus, could be sidelined for several more weeks.