A full-blown bailout for Spain is all but inevitable as it has lost control of its debt crisis, analysts say, despite Madrid's insistence that it does not need rescuing.

Spain's Minister of Treasury and Civil Services Cristobal Montoro 

With eurozone ministers set for the first of several key meetings over Spain Thursday, its budget minister insisted the country was stable despite soaring borrowing costs and a 100-billion-euro lifeline thrown out for its banks.

"Spain has not been rescued because it does not need to be rescued," minister Cristobal Montoro told parliament Wednesday.

But analysts warned Spain may not stay afloat without direct financial aid from its European neighbours.

"A sovereign bail-out is all but inevitable," wrote Capital Economics chief European economist Jonathan Loynes.

"The recent further rise in Spanish government bond yields underlines the fact that the banking bailout will not address the country's broader fiscal problems."

Greek elections on Sunday averted the immediate threat of Athens exiting the eurozone, but concern over Spain did not ease.

It paid high borrowing rates to investors in a sale of 12- and 18-month debt Tuesday. The yield on its benchmark 10-year bonds passed the 7.0-percent danger mark on Monday and on Wednesday was around 6.8 percent.

"These borrowing costs are unsustainable and at this level Spain is on track to require a full bailout" unless its debts are underwritten by eurozone partners or the European Central Bank buys its debt, said Kathleen Brooks, research chief at brokerage Forex.com.

Spain's Prime Minister Mariano Rajoy demanded "urgent" action by the European Union to calm market tension, in a letter to its leaders at the start of June.

He insisted the European Central Bank must play a role by providing liquidity.

But action by the ECB to help keep Spain's borrowing costs down "is far from certain given the ECB's reticence", Loynes warned. The onus is on political leaders ahead of a European Union summit on July 28 and 29.

Marian Fernandez, financial director at investment group Inversis, added: "We do not think the ECB is going to do anything before next week's summit. They have said the ball is in the politicians' court."

Spain, the eurozone's fourth-biggest economy, is expecting Thursday to receive the results of tests by two firms of private auditors to determine how much it needs to borrow under the deal to stabilise its banks.

Madrid is expected to transmit an official request for that aid to its partners at a eurozone finance ministers' meeting in Luxembourg on Thursday, a European Union diplomat said in Brussels.

Then on Friday leaders of Spain, Italy, France and Germany meet in Rome to thrash out a common position on the debt crisis ahead of the full summit in Brussels.

Spain also faces its next debt market test on Thursday, when it will try to raise up to two billion euros in a mix of two-, three- and five-year bonds.

Angel de Molina, an analyst at brokerage Tressis, said the financial markets on which Spain borrows money to finance its activities are "sensing a lack of action and political leadership" in Europe.

"The European Union and the European Central Bank both have to send this message to the markets: we are here to do what we have to do," he said.

As leaders debate roundabout ways of easing pressure on troubled countries by investing European aid funds without carrying out a direct rescue, time may be running out, analysts warn.

"At the rate its yields are rising, Spain doesn't have enough time to wait for Europe's politicians to decide whether or not to underwrite the debts of the weakest states," said Brooks.

"It needs action now."