Lithuania was the first country to ratify the ill-fated EU constitution
The Latvian and Lithuanian parliaments have approved the EU's Lisbon Treaty which aims to reform decision-making in the 27-member bloc.
The votes were welcomed by European Commission President Jose Manuel Barroso who said the treaty had moved a step closer to taking effect in 2009.
Thirteen parliaments have given the treaty their support so far.
On 12 June, the Irish Republic will hold a referendum, the only EU state to put the treaty to a public vote.
Opinion polls suggest a third of the electorate is undecided about how to vote.
LISBON TREATY PROGRESS
Parliamentary approval: Hungary, Malta, Slovenia, Romania, France, Bulgaria, Poland, Slovakia, Portugal, Denmark, Austria, Lithuania and Latvia
Approval expected by summer: Estonia, Belgium, Luxembourg
Referendum: Irish Republic
Challenges: Legal objections in Czech Republic, Germany and UK
No date: Cyprus, Finland, Greece, Netherlands (held up by referendum proposal), Italy (new government), Spain (new government, Sweden
In the Lithuanian parliament, 83 MPs in the 141-member chamber voted in favour of the treaty, while 70 MPs backed it in Latvia's 100-seat house.
Both countries joined the EU in 2004 and Lithuania was the first member state to ratify the ill-fated EU constitution in November 2004, months before it was rejected by voters in France and the Netherlands.
The treaty has to be ratified by every member state before it can come into effect.
As well as aiming to streamline decision-making in the bloc, the treaty also provides for a president for the European Council and a High Representative to co-ordinate foreign policy.