Spain has concluded a controversial arms deal with Venezuela to supply military equipment worth $2bn.
The ceremony was shown on Venezuelan state television
The signing in Caracas was attended by Venezuelan President Hugo Chavez and Spain's Defence Minister, Jose Bono.
Under the deal, Spain will supply eight navy patrol boats and 12 military transport planes to Venezuela.
The United States had tried to block the signing for the last week, saying that Mr Chavez is a source of instability in the region.
During the ceremony, which was broadcast on Venezuelan state TV, President Chavez said attempts by Washington to sabotage the deal were an example of the US trying to impose its will over the world.
Both Venezuela and Spain insisted the equipment was for peaceful purposes. Mr Chavez said it would be used to combat the drug-trafficking in the Venezuelan-Colombian border.
US ambassador Eduardo Aguirre had asked the Spanish authorities not to go ahead with the sale.
He said Washington was considering whether to allow Spain to sell aircraft made with US technology, which would require a US export licence.
Venezuela said the military equipment would help border security
But Madrid said the deal had been negotiated with "scrupulous respect for international law".
Speaking in Caracas, Mr Bono said Spain was a "sovereign and autonomous country" and that there was not any embargo in place barring the sale.
The arms deal was agreed during Spanish Prime Minister Jose Luis Rodriguez Zapatero's a two-day visit to Venezuela last March.
President Chavez said at the time that the boats would be used to step up Venezuela's coastal patrols against the drugs trade, while the transport planes would be used mainly for humanitarian missions inside and outside the country.
Tensions between Washington and Caracas have grown in recent months, in part because of US criticism over Venezuela's purchases of military equipment.
Earlier this year, the South American country signed deals for Brazilian aircraft, and for Russian automatic rifles and helicopters.