Eurozone ministers Friday hailed a deal to boost their firewall against the debt crisis to more than a trillion dollars but analysts were quick to pounce on "window dressing" to pad out the figures.

Under intense international pressure to combat the two-year crisis and with fresh Spanish budget woes underscoring the need not to let down their guard, finance ministers sealed an agreement aimed at reassuring financial markets.

"All together, the euro area is mobilising an overall firewall of approximately 800 billion euro, more than $1 trillion," said a joint statement from the 17 finance ministers of the eurozone bloc.

However, on close inspection, it turned out that some 300 billion euros of the headline figure was composed of loans already pledged to debt-wracked countries, giving only 500 billion euros in untapped funds.

And ministers agreed that the maximum lending capacity of the new combined bailout pot would be 700 billion euros, with the extra 100 billion euros coming from already pledged bilateral loans and a special EU fund.

"It is a load of window dressing," Carsten Brzeski, senior economist at ING bank in Belgium, told AFP.

The deal is a "classic European compromise" with extra elements added on "to present the one trillion number to financial markets," he said.

Nevertheless, European and US stock markets were firmer Friday after news of the deal but investors remained wary.

Holger Schmieding, chief economist at Berenberg Bank, said "the actual effect of today's decision is limited.

"Markets could still be unimpressed by the firewall's limitations," he said.

Ministers seemed to insist on the figure of one trillion dollars, with Ireland's Michael Noonan calling it a "very serious firewall."

Highlighting the need to strengthen the euro's defences against a possible spreading of the crisis to economies such as Italy and Spain, the government in Madrid agreed a new budget with sweeping cuts to reduce its deficit.

Spain's budget for 2012 includes over 27 billion euros in savings, Deputy Prime Minister Soraya Saenz de Santamaria said.

The EU's top economic official Olli Rehn acknowledged on the sidelines of the meeting that Spain was in "a very difficult situation."

The new budget in Spain was reached against a backdrop of a general strike which turned violent at times amid protests against austerity measures and labour market reforms.

Spanish borrowing costs have risen in recent weeks after Madrid admitted it had missed its 2011 deficit target of 6.0 percent of gross domestic product, reporting 8.5 percent instead.

And in a reminder that the crisis has not disappeared from where it started, Greece's leader unnerved ministers by raising the spectre of a third bailout package for his debt-mired country.

Ministers were under huge international pressure to clinch a deal that top and emerging G20 economies have said is the precondition for boosting their own lending to the International Monetary Fund to aid the eurozone.

Schmieding said that with the deal, the eurozone "will probably be able to obtain additional commitments from the IMF and the G20 to complement the European rescue efforts."

But even the 800 billion euros package falls short of what was demanded by the Organisation for Economic Cooperation and Development, which called for one trillion euros -- what head Angel Gurria called the "mother of all firewalls."

It also fell well short of demands by the European Commission and France, who wanted something closer to 940 billion euros but came up against German resistance.

Facing vital state elections and a public tired of bailing out the eurozone, Chancellor Angela Merkel has insisted that the maximum capacity of the combined rescue funds should not exceed 700 billion euros.

Even the communication of the deal resulted in somewhat of a farce.

To reporters' surprise, Austrian Finance Minister Maria Fekter left the closed-door meeting, marched into the media centre and revealed the 800-billion-euro agreement.

But this infuriated the head of the Eurogroup, Luxembourg Prime Minister Jean-Claude Juncker, who was due to announce the deal at a news conference minutes later.

Juncker, said by one EU diplomat to be "furious" at the leak, promptly scrapped the news conference.

Fekter later apologised, sources said.

But it was not clear whether Juncker, a veteran of hundreds of EU meetings, was mollified.

"If you reveal decisions when they have not yet been taken, then I don't need to do a press conference," he told French daily Le Monde.