Mr Lenihan also said while it is envisaged the loan will amount in total to €1.3bn, provision has been made in the legislation for an upper limit of €1.5bn.
The Minister was speaking during a Dáil debate on the legislation which will give affect to the transaction.
The loan is part of an EU rescue plan to stabilise Greece and the euro.
Mr Lenihan also said Ireland will not be financially disadvantaged by the loan and it will not be included in the overall national deficit.
On the domestic front, the Minister said there were signs economic activity was picking up and that 'we are about to turn a corner.'
He said the tough decisions taken by the Govt over the past two years have been vindicated.
Fine Gael's Richard Bruton said he supported the loan to Greece, but added there must be robust scrutiny of whether or not the measures work.
Greece recieves first tranche
Ten eurozone countries have paid €14.5bn in bilateral loans to Greece - the first tranche of a €30bn loan agreement to help stabilise the Greek government debt position.
Ireland did not contribute to the first tranche of funding - neither did Belgium, Finland, Slovenia or Slovakia.
Legislation allowing Ireland to lend funds to Greece goes before the Dáil today, and is due to conclude all stages by tomorrow evening.
European Union finance ministers have been meeting in Brussels amid uncertainty over the euro and disagreements over the future governance and co-ordination of the EU's 27 economies.
Differences of opinion have also emerged about how to apply the rules governing the €750bn rescue fund agreed last week following fears that the Greek debt crisis could spread.
Getting agreement between the International Monetary Fund, the European Commission and the eurozone countries on the rescue package may have been the easy part.
There are still sharp differences over how the money should be released should a eurozone member get into trouble.
There are also differing views on the extent to which the EU's economies should be more tightly co-ordinated in order to avoid a repeat of the Greek debt crisis.
At a meeting of the 16 eurozone finance ministers last night, countries such as Finland and Germany wanted national parliaments to debate whether a country should receive rescue money if they seek help.
But that was frowned upon by the chair of the euro group, Luxembourg president Jean Claude Juncker, who said he thought all countries had already agreed on the mechanism.
However, it looks as if any country seeking help will need the unanimous backing of all the eurozone countries.
Following the meeting, Mr Juncker insisted that the euro was a credible currency, although he was concerned at the speed of its fall in the currency markets.
Yesterday, the euro fell to its lowest level against the dollar since 2006 in Tokyo trading.
It recovered slightly, but it was still under pressure in early trading this morning.
Finance ministers have reached agreement on tighter restrictions for hedge funds and private equity firms.
They will now negotiate with the European Parliament to draft new legislation.
