Kyoto seeks to limit humans' influence on the climate
Ratification of the treaty itself now goes to the European Council of heads of state and government, which could take the action as early as the EU summit in Barcelona, Spain, this month.
The ministers' agreement was reached at a meeting in Brussels.
"This means that the EU will complete the ratification [process] by 1 June," said European Commission spokeswoman for environmental protection Pia Ahrenkilde-Hansen.
Diplomatic offensive
The protocol, the first details of which were agreed in the Japanese city of Kyoto in 1997, commits the EU to reduce its emissions of greenhouse gases - gases that warm the atmosphere - by 8% of 1990 levels during the five-year period 2008-2012.
The primary gas covered by the protocol is carbon dioxide, which is emitted as a byproduct of many industrial processes and when oil, coal and gas are burned.
To have legal status, Kyoto must been ratified by 55 countries responsible for 55% of the emissions in 1990. Because the US, the "world's biggest polluter", has rejected the protocol as damaging to its economic interests, all the other developed countries must push on with the process for it to come into force.
Since the US pullout, the EU has led a diplomatic offensive to ensure countries such as Russia, Japan and Canada stick with Kyoto. Those countries have said they will ratify but have yet to do so.
Green campaigners would like to see Kyoto ratified by the World Summit on Sustainable Development later this year.