Spanish parliament is to ask the government to approve the Great Ape Project, which would mean recognising that our closest genetic relatives should be part of a "community of equals" with humans, supporters of the resolution said.
Backers of the resolution expect support from the Socialist Party of Jose Luis Rodriguez Zapatero, Spain's prime minister, whose government has legalised gay marriage and reduced the influence of the Catholic Church in education.
"With this, Spain will make itself a world leader in protection of the great apes," said Pedro Pozas, general secretary of the Great Ape Project's Spanish branch.
The resolution was initially due to be voted on on Wednesday but was postponed due to a tight parliamentary agenda, probably until September, said the Green Party parliamentarian who proposed it, Francisco Garrido.
However, the proposal prompted criticism and some ridicule at first.
Spanish media quoted the Catholic Archbishop of Pamplona as saying it was ludicrous to grant apes rights not enjoyed by unborn children, in a reference to Spanish abortion laws.
"We are in favour of defending animals, but people come first"
Father Santos Villanueva, spokesman for Archbishop of Pamplona
But a spokesman for Archbishop Fernando Sebastian said he had been taken out of context and now supported the resolution.
"We are in favour of defending animals, but people come first," Father Santos Villanueva said.
Philosophers Peter Singer and Paola Cavalieri founded the Great Ape Project in 1993, arguing great apes - chimpanzees, gorillas, orangutans and bonobos - were so close to humans that they deserved rights to life, freedom and not to be tortured.
"When a loved one dies, they grieve for a long time. They can solve complex puzzles that stump most two-year-old humans," said Singer.
Setting a precedent
The Spanish move could set a precedent for greater legal protection for other animals, including elephants, whales and dolphins, said Paul Waldau, director of the Centre for Animals and Public Policy at Tufts University.
"We were born into a society where humans alone are the sole focus and we begin to expand to the non-human great apes," he said.
"It isn't easy for us to see how far that expansion will go, but it's very clear we need to expand beyond humans."
There are only a few hundred apes in Spain, mainly chimpanzees.
However, the resolution would also push the government to help endangered populations in Africa and Asia, added Pozas.