"It'll be a complicated process," Chivvis said of a possible increase in European defense spending, citing questions of spending allocation, budget limitations and competing governmental commitments.
Italian Prime Minister Mario Renzi said Wednesday that his nation should be given the same European Union budgetary allowances as France. But those comments appear to refer only to the country's existing budget proposals.
Renzi's government has warned that IS could attack Rome during a Roman Catholic Holy Year beginning next month.
The previously submitted French draft budget for 2016 was considered "broadly compliant" with EU fiscal rules, although the European Commission had warned France against risks of missing the agreed spending targets in a report prepared before the Paris attacks.
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Hollande announced earlier this year, a few months after the deadly attack on satirical magazine Charlie Hebdo and a kosher supermarket, that he planned to increase military spending over the next four years by 3.8 billion euros ($4.04 billion). Although the French president called the increase "significant," some military analysts and French lawmakers said it did not go far enough to combat terrorism.
While European and North American leaders talk about the fight against ISIS, Chivvis and Lamrani said that a primary driver of defense spending over the next few years may be concern about a Russian move against Eastern Europe.
Euro zone finance ministers plan to gather in Brussels on Monday for an extraordinary meeting to assess the draft budgets of the 19 countries sharing the euro.
— Reuters contributed to this report.