PFA Scotland is helping "the majority" of Hearts players in negotiations over "substantial wage deferrals".
All Hearts staff have until 17:00 GMT on Wednesday to respond to the club's request that they accept a 50% pay cut.
Should they refuse, Hearts can invoke contract clause 12 - an option available to all Scottish Premership clubs - and suspend salaries.
"The players recognise the club's cash flow problems as a result of COVID-19," said a players' union statement.
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"They wish to assist the club through these difficult times by offering to negotiate substantial wage deferrals.
"Player contracts cannot be terminated, or altered unilaterally, but the union is more than willing to assist in negotiating agreements between clubs and players.
"In addition, our position is should clubs reduce the wages of existing players on valid agreed contracts, and then use the sums saved to sign new players in August, that would be wholly unfair."
Hearts captain Steven Naismith has said publicly he will accept the 50% pay cut, while manager Daniel Stendel has wavied his salary and defender Clevid Dikamona has exercised the right to cancel his contract.
The Tynecastle club have also confirmed that "the majority of non-football employees" have been placed on furlough.
PFA Scotland also says clubs "across the country" have begun negotiations with players over wage deferrals alongside participation in the government's job retention scheme, which pays 80% of wages up to £2,500 per month.