One thousand people are expected to mark the murders of two Ulster Defence Regiment (UDR) soldiers in a 1988 IRA bomb attack during a rally in Belfast city centre on Saturday.
Ulster Unionist leader Mike Nesbitt urged loyalist protesters to cancel their concurrent demonstration against restrictions on the Union flag flying from Belfast City Hall this weekend.
He said nothing should deflect from marking the memory of two "brave citizens".
Mr Nesbitt said: "I understand over 1,000 people will take part in the parade to commemorate James (Cummings) and Fred (Starrett), who were members of the Ulster Defence Regiment deployed to protect the building site that was to become CastleCourt Shopping Centre.
"Given the cost of the flags protests, it would be regrettable if those involved did not take the opportunity to step back to allow the media to highlight how republicans once stopped at nothing to pursue their economic war against Northern Ireland, irrespective of the cost in terms of human lives or impact on the economy.
"The cost of the current protests cannot be justified, but are as nothing to the equally unjustifiable cost of the Troubles."
James Cummings and Fred Starrett were killed by an IRA bomb in Royal Avenue on February 24 1988.
A campaign of loyalist street protests has been taking place since December 3, when Belfast City Council voted to reduce the number of days the Union flag is flown at City Hall.
Mr Nesbitt told the BBC: "I appeal to people like (protest leader) Jamie Bryson to use their influence to call off Saturday's protest and leave the streets clear for the parade in commemoration of Privates Cummings and Starrett.
"I further call, as I have since the first week of December last, for the flags protests to move off the streets. It is clear to all that the issues go far beyond the Union flag, and I repeat my invitation to Mr Bryson and his colleagues to engage with the Unionist Forum, which offers a unique opportunity to air their grievances with the realistic hope of redress."