As part of the eurozone Latvia, like other countries in the single currency bloc, would need to approve a deal before it could be implemented.
Any such decision concerning a third Greek assistance program would likely be adopted in August, provided Greece implements wide-ranging reforms in coming days, Reirs said.
Greece has until Thursday to adopt amendments to several laws providing for reforms on value added tax, pensions, the labor market and privatizations, with reports suggesting the German Bundestag is set to vote on whether to support a new bailout as soon as Friday,
However Reirs pointed out various other institutions also need time to approve the package including the International Monetary Fund, European Central Bank and the European Commission - process likely to take "four to six weeks" according to Reirs.
Consequently, Latvia's contribution to the European Stability Mechanism (ESM) for the Greek bailout - which could amount to around €240m - could be decided no earlier than August, Reirs told LETA.
Asked whether, if Greece does not accept the necessary amendments to the law in coming days, it would be expected to withdraw from the eurozone Reirs said: "Practically - yes."
"We believe that the time for blackmail and scaremongering has passed," said Reirs.