The favoured option being discussed is that the existing European rescue fund, the EFSF, would purchase Spanish government bonds at primary auctions while the European Central Bank would intervene in the secondary market to lower yields, the sources said.
No specific figure for aid has been discussed in the talks, which started several weeks ago, one of the sources said.
Other senior eurozone sources were more cautious, one saying nothing clear-cut had emerged on aid for Spain.
A fifth said no talks were going on at all.
Spain’s prime minister’s office declined to comment.
A spokeswoman for the economy ministry said there was no change in the Spanish position, which is that it would wait until the next meeting of the governing council of the ECB on Sept 6, hoping for details on how the ECB plans to intervene, before deciding on any move.
ECB president Mario Draghi has said the central bank could intervene to lower painfully high yields, but only if the country concerned asked for similar help from the bloc’s rescue fund first.
The three sources who spoke with Reuters yesterday said the negotiations were focusing on conditions attached to the aid, which would be included in a memorandum of understanding.
While there is a political consensus that the conditions should be limited to what is already included in EU recommendations to Spain, which has pushed through a raft of painful austerity measures, two of the sources said eurozone countries were insisting on setting up a tougher schedule of monitoring.
Separately, two of the sources said Spain’s eurozone partners and the European Commission had dashed its hopes of getting an emergency liquidity line for its banks before the first tranche of up to €100bn of aid was disbursed in the autumn.
Spanish authorities had hoped to receive up to €30bn in August to start recapitalising state-rescued banks, such as Bankia, CatalunyaCaixa and NovaGalicia.