CARACAS (Dow Jones)--Venezuela's bolivar dropped Tuesday against the dollar after state-oil company Petroleos de Venezuela SA, or PdVSA, sold less than half of a $3 billion bond offer, disappointing investors who expected a stronger injection of U.S. currency.

The bolivar weakened to VEB6.65 in parallel trading, the lowest rate since PdVSA announced that the bond would be allowed to trade abroad.

On Monday PdVSA said that the auction had a cut-off price of 175% of the bond's zero-coupon face value. The auction resulted in a sale of only $1.41 billion from the $3 billion offer.

"The offer wasn't directed at lowering the rate. The government wanted to raise funds for PdVSA," said Abelardo Daza, an economics professor at IESA, a Caracas-based business school IESA.

Investors and companies that purchased the PdVSA bonds will now be able to buy the bonds using bolivars and sell them in exchange for U.S. currency.

The high offer price for the bonds, however, "does not suggest attractive secondary market prices, which questions the offshore participation," Siobhan Morden, an analyst with RBS, wrote in a report.

The parallel currency market in Venezuela has become an essential cog in the country's economy, with a growing number of companies buying dollars at the unofficial rate as the government is further restricting the sale of U.S. currency at a VEB2.15 peg.

-By Darcy Crowe, Dow Jones Newswires; (58) 212 905 6304; darcy.crowe@dowjones.com