The leaders of Fianna Fáil and Fine Gael have told the Social Democrats that nobody knows with any accuracy how long the health emergency will last.
They said the timing of any economic recovery or what form Brexit will take is also unclear.
Micheál Martin and Leo Varadkar were responding to a request for information from Catherine Murphy and Roisin Shortall.
In a joint letter they said the next government would seek to borrow at affordable rates to fund the deficit in order to avoid the need for austerity and to stimulate an economic recovery.
The two party leaders said they believed this was possible given the current EU and European Central Bank policies.
Their objective was to reduce the deficit gradually once the economy returned to growth, they said.
When this happens the government would aim to eliminate borrowing for current spending while continuing to borrow for capital projects in the areas of health, housing and climate action.
An update of the latest economic forecast for the country is set to be published by the Department of Finance in the coming days.
As work continues on forming a government, tomorrow the internal FIne Gael reference group chaired by Richard Bruton is meeting to discuss policy priorities following on from the publication of the framework document.