COPENHAGEN — European finance ministers agreed Friday to create a permanent bailout fund for the euro zone with temporary lending capacity of €800 billion, the latest signal sent by Europe to show its determination to overcome a two-year-old crisis of confidence.


The decision gives Europe a so-called firewall against future crisis with a lending capacity near the symbolic level of $1 trillion.


“Finally, robust firewalls have been established," the group of countries that use the euro said in a statement.


But the euro zone agreed to combine the firepower of some existing bailout funds to reach a headline number that is much larger than the originally planned sum of €500 billion.


The new figure of €800 billion includes large slices of money that already has been deployed to help countries including Greece, and that sum was expected to be capped at €700 billion by the second half of next year.


Questions are likely to persist about whether the size of the fund would be sufficient to deal with crises in major European economies like Spain and Italy, were they to require financing on the scale already provided to stabilize markets in Greece, Ireland and Portugal.


In their statement, the so-called Eurogroup of countries that use the currency also said members had committed to provide an additional €150 billion in contributions to the International Monetary Fund.


But it was also unclear on Friday afternoon whether the sum was big enough to nudge donors to the I.M.F. including the United States and China, to pledge more to the fund. That would give the fund, which has taken part in the three euro-zone bailouts, even more resources to help bail out other European countries, if necessary.