Yields on Spanish 10-year bonds have risen past 6.5 per cent on the secondary market.
They stood at 6.52 per cent early today after closing at 6.4 per cent the previous day. The rate is now 4.73 percentage points above the equivalent German bond yield.
Investors were keenly awaiting a Treasury auction of up to 4 billion euros in 10-year bonds, with interest rates expected to be high.
Spain's chapter of the European debt crisis has engulfed the campaign for general elections, due Sunday.
Oppostion conservatives are expected to score a landslide win over the ruling Socialists, saddled with an economy that has 21.5 unemployment and posted zero growth in the third quarter. The forecast for next year is just as gloomy.