PARIS, France (AP) — Seeking to restore confidence in the euro, the leaders of France and Germany jointly have called for changes to the European Union (EU) treaty so that countries using the euro would face automatic penalties if budget deficits ran too high.

But not everyone on Wall Street was reassured that Europe would get control of its two-year-old debt crisis.

Stock prices rose and borrowing costs for European governments dropped sharply in response to the changes proposed yesterday by French President Nikolas Sarkozy and German Chancellor Angela Merkel. But some of the optimism faded late in the day when Standard and Poor’s threatened to cut its credit ratings on 15 eurozone countries, including the likes of Germany, France and Austria which have been considered Europe’s safest government debt issuers.

The announcement came only hours after Sarkozy and Merkel revealed sweeping plans to change the EU treaty in an effort to keep tighter checks on overspending nations. The proposal is set to form the basis of discussions at a summit of EU leaders on Thursday and Friday that is expected to provide a blueprint for an exit from the crisis.

While the Franco-German plan would tie the 17-eurozone nations closer together, a tighter union would likely also result in heavier financial burdens for the region’s stronger economies, which have already put up billions of euros to rescue Greece, Ireland and Portugal.

Analysts noted that the proposals did not foresee a clear roadmap on how to get the eurozone economies growing again and to reduce funding costs for struggling nations in the long term.

“If this is all we get it’s really very bad news for the future of the euro,” said Simon Tilford, chief economist at London’s Centre for European Reform.

Many analysts have called on the European Central Bank to intervene in debt markets to lower struggling countries’ borrowing costs or the creation of eurobonds — debt backed by all 17 euro countries.

“The onus is still on the ECB to print money to make huge loans or bond purchases and draw a line under the crisis,” said Jennifer McKeown, senior European economist at Capital Economics.

The euro fell after the S&P announcement, trading down 0.1 per cent at US$1.339, and trading in futures on the S&P 500 and Dow Jones Industrial Average turned negative.

After the New York markets closed, S&P confirmed that it had placed 15 nations on notice for possible downgrades. Only two countries that use the euro weren’t affected: Cyprus already had that designation and Greece already has ratings low enough to suggest that it’s likely to default soon anyway.

France and Germany, the eurozone’s two largest economies which currently both have an AAA-rating, quickly came out against the S&P move.

“Germany and France reaffirm that the proposals they made jointly today will reinforce the governance of the euro area in order to foster stability, competitiveness and growth,” they said in a joint statement. “France and Germany, in full solidarity, confirm their determination to take all the necessary measures, in liaison with their partners and the European institutions to ensure the stability of the euro area.”

Stocks had risen after the leaders of France and Germany called for a new treaty to impose greater fiscal discipline on European countries. Yields on Italian government bonds receded sharply after the new premier Mario Monti introduced sweeping austerity measures over the weekend. That suggests traders believe Italy is less likely to default.

Investors are hoping that the summit of European leaders on Thursday and Friday will produce concrete measures to prevent a messy break-up of the euro currency, which is shared by 17 nations. Markets have been jittery because of fears that the euro might disintegrate, causing a sharp recession in Europe that would spread through the world economy.

“Our wish is to go on a forced march toward re-establishing confidence in the eurozone,” Sarkozy said at a news conference in Paris yesterday, with Merkel at his side. “We are conscious of the gravity of the situation and of the responsibility that rests on our shoulders.”

EU treaty changes could take months, if not years, to implement and don’t wipe away the mountains of government debt dragging down Europe’s economy. But preliminary buy-in Friday from the 17 countries that use the euro could set the stage for further emergency aid from the European Central Bank, the International Monetary Fund or some combination.

“The onus is still on the ECB to print money to make huge loans or bond purchases and draw a line under the crisis,” said Jennifer McKeown, senior European economist at Capital Economics. “Perhaps if other member states sign up to Merkel’s and Sarkozy’s proposals this week the (ECB) will step in.”

Sarkozy pledged to have a revised EU treaty ready for signing by March. It would then need to be ratified in each country, which could mean lengthy parliamentary debates or national referendums in some cases.

“A lot depends on the specifics and how these are going to be framed by lawyers,” said Piotr Maciej Kaczynski, an expert on EU constitutional issues at the Centre for European Policy Studies in Brussels.

At the very least, it could take at least 18 months to ratify a new treaty once it has been signed by all heads of state, said Kaczynski. “That is a much longer timeline than what markets might want,” he said.