SFA chief executive Stewart Regan expressed his sympathy for under-fire referees, who took their stance amid safety fears, and vowed to reach a resolution to avert this weekend's action.

But he has already begun the process of finding referees to take their place for this weekend's matches in the Clydesdale Bank Premier League and other senior fixtures.

A statement from Regan read: "While we remain hopeful that the situation can be resolved to everyone's satisfaction, we have no option but to draw up contingency plans, which will involve sourcing match officials in other countries."

He later told Sky Sports News: "We will seek to source officials from other countries across Europe, FIFA-listed officials or officials from the premier leagues in each of those respective countries and we will try to source enough officials to ensure the matches can go ahead.

"At this stage we are not in a position to talk about which countries they would come from. We are in very early-stage discussions with other associations across Europe.

"We have the backing of the Scottish Premier League to take that action and we are waiting for our own referee committee to approve that action."

Referees acted unanimously at their monthly meeting on Sunday amid fears one of them would come under physical attack after a number reported being threatened at home, in the street and the workplace.

A statement issued to Press Association Sport on behalf of category one referees read: "The meeting concluded that the incessant and adverse nature of recent comments on referees has placed intolerable pressures on personal and professional lives, with the view expressed that statements questioning honesty and integrity have been aimed across refereeing in general and have led to an unprecedented level of abuse and genuine concerns for safety and for the ability to carry out normal family and business commitments.

"The group appreciated the full impact this decision will have on fans this weekend and for that reason it was not taken lightly.

"However, it was believed to be necessary in the current climate and will hopefully put an end to the more extreme attacks on referees."

SPL chief executive Neil Doncaster expressed his disappointment that the referees had called their strike out of the blue.

"We have had no dialogue with the referees and that's one of the most disappointing things," Doncaster told Sky Sports News.

"The first thing I heard was that I got a call last night telling us there would be a strike. There is a right way to go about it and simply calling a strike is the wrong way.

"It has to be preceded by some conversations about concerns and no-one has come to us with any concerns."

Doncaster is determined that supporters will be able to watch their teams play this weekend.

"What is important is that the games go ahead," he said. "We have to put supporters first.

"It costs a lot of money and time to follow a club and to have this inconvenience thrown in their way is very, very unfortunate indeed."

Doncaster backed the SPL's contingency plans, which look certain to be focused abroad.

It is understood that category two officials backed their colleagues on Sunday, although they plan to officiate games in the junior leagues.

However, lower-grade officials are unlikely to break the strike and some referees from abroad may think twice.

There have been suggestions that the SFA could look to the Republic of Ireland as the Airtricity League is in its close season.

But the Football Association of Ireland would broach the matter with their referees before committing.

An FAI spokesman told Press Association Sport: "If there is an official request we we will consider it, but obviously we would have to consult with our referees first."

The Football Association of Wales claimed it was highly unlikely they would be able to help out given their league is in full flow, while it is understood the Premier League do not have sufficient numbers of officials themselves to offer help elsewhere.

Meanwhile, SFA president George Peat called for an end to the attacks on referees' integrity.

Peat said: "Unfortunately the behaviour of some people in recent weeks has tarnished the image of Scottish football. It has demeaned the game.

"The culture of inference, innuendo and conspiracy theories must stop."

Peat did not name any clubs but there was little doubt he was referring to Celtic, whose chairman John Reid last week called for the SFA to sack Dougie McDonald over his admission that he misled Celtic manager Neil Lennon over the circumstances surrounding his penalty U-turn at Tannadice on October 17.

Asked about Reid's intervention, Peat said: "We haven't even discussed that but the comments certainly weren't helpful.

"I don't want to personalise this, I'm just talking about comments which have been made recently which have not helped."

Celtic have remained at the centre of controversy since the Tannadice incident, with Lennon also critical of Willie Collum and Craig Thomson following defeats to Rangers and Hearts.

Forward Gary Hooper also called for McDonald to quit and speculated that referees might discriminate against his team in order to boast they had given a decision against what he called one of the biggest clubs in the world.

Celtic have not made any official comment on unsourced reports that they welcome the strike action in the hope that it leads to an independent inquiry and UEFA intervention.

But a UEFA spokesman told Press Association Sport: "This is a purely domestic matter."