European Union newcomers Estonia, Lithuania, and Slovenia became the first of the bloc's 10 new member states to join the exchange rate mechanism that will help them prepare for euro entry.
The three states join a grid known as ERM-2, whose only member has been Denmark since Greece adopted the single currency in 2001 after spending about three years in the regime.
European Commissioner Siim Kallas hailed the news but also stressed that ERM-2 entry was only one of the steps towards euro entry and that more work lay ahead.
"My reaction is positive but this is just part of a bigger process. The countries have made some commitments during the negotiations and it makes discipline in monetary and fiscal affairs stronger," Estonia's Mr Kallas told Reuters.
"There will be tough monitoring of the situation and the realism of the convergence programmes" which are the medium-term budget plans submitted to the European Commission and EU finance ministers for their assesment.
This echoed the advice issued after the highly secretive meeting that was attended by finance officials from the dozen euro zone countries, the European Central Bank, Denmark, and the three countries that had applied for ERM-2 entry.
All three ERM-2 entrants were urged to pursue sound fiscal policies, with Slovenia also advised to take steps to lower inflation in a sustainable way.
The ECB and the central banks of the three countries that joined the ERM-2 will issue details of the exchange rates at which intervention in the foreign exchange markets is compulsory.
The Slovenian tolar will trade in the normal fluctuation bands of ERM-2, which are plus or minus 15 per cent around a central parity rate, which was set at 239.640 per euro.
Lithuania and Estonia joined ERM-2 with their existing currency board arrangements in place, but statements said this was a unilateral commitment and placed no additional obligation on the ECB to intervene in the foreign exchange markets.
The Estonian kroon's central rate in ERM-2 was fixed at 15.6466 per euro, as had been widely expected given this was the rate at which the kroon had been pegged to the euro since 1999 under a currency board regime.
The Lithuanian litas' ERM-2 central rate was set at 3.45280 per euro, the same rate at which the currency has been pegged to the euro since February 2002 under a similar currency board arrangement.
The main elements of a currency board regime are an exchange rate that is fixed to an anchor, the domestic currency can always be exchanged at this fixed exchange rate, and that the central bank has a long-term commitment to the system, which is often set out in the bank's law.
Other states, such as Cyprus and Malta, are expected to follow suit and join ERM-2 in the next six to seven months.
Mr Kallas declined to comment on how many other countries would follow Estonia, Lithuania, and Slovenia into the ERM-2 this year and said this was a decision for each member state.
"Each country must (then) be assessed on its own merits," he added.
Slovenia, the only one of the new ERM-2 entrants which does not have a currency board regime, was told to curb inflation.
"The agreement on participation of the tolar in ERM-2 is based on a firm commitment by the Slovenian authorities to continue to take the necessary measures to lower inflation in a sustainable way," a statement said.
It also warned of the need to ensure domestic cost developments, in particular wages, were in line with productivity growth.
The country's prime minister, Anton Rop, told reporters in Ljubljana that the government would work to ensure a stable macroeconomic situation, a message echoed by the central bank.
"This (ERM-2) entry means an obligation on the government and the Bank of Slovenia for a further lowering of inflation..., while the Slovenian economy will enjoy a more stable economic environment," said Central Bank Governor Mitja Gaspari.
Estonia was told to take steps to contain domestic credit growth, ensure effective financial supervision, and push on with structural reform to help maintain the overall competitiveness of the economy. Similar recommendations were made for Lithuania.