(Adds comment from minister in paragraph 7)
By Sonya Dowsett
MADRID, May 16 (Reuters) - Spain signalled on Tuesday that satellite business Hispasat is a strategic asset which will be monitored if its majority-owner Abertis is bought by Italy's Atlantia.
Atlantia's 16.3 billion euro bid ($18 billion) for Abertis, which would create the world's biggest toll road operator, resuscitated a similar cross-border merger which fell through 10 years ago due to opposition from the Italian government.
Abertis and its biggest shareholder, Criteria, said on Monday they would consider the bid but it may take months to respond. Criteria will seek the opinion of the government and other institutional investors before making a response, sources with knowledge of the matter said on Monday..
The Spanish government would not interfere in the Italian infrastructure company's offer for Abertis, which was a matter between private companies, Spain's Economy Minister Luis de Guindos told journalists after an event in Barcelona.
However, Hispasat, competition law and the future of Abertis-owned road concessions in Spain that are about to expire are points of interest for the Spanish government.
"Everything surrounding Hispasat will be carefully studied. It is a strategic asset for the government. It has its own set of rules and implications," de Guindos said.
The Public Works Minister, Inigo de la Serna, said on Tuesday that aside from needing approval from Spanish competition and market authorities, any purchase of Abertis by Atlantia needed government approval due to implications for Spanish motorway concessions owned by the government and granted to Abertis and due to the future implications for Hispasat.
Hispasat controls Spain's national satellite communications system. Abertis has a 57.05 percent stake, while the government owns more than 9 percent through public companies.
Alongside competition law, other points of national interest could be the future of Spanish motorway concessions owned by Abertis that are up for renewal soon, de Guindos said.
Atlantia Chief Executive Giovanni Castellucci said on Tuesday it was now up to the Spanish to decide.
"I will relax only after the Spanish market authority and Abertis board have given their green light (to our takeover offer)," he told Italian newspaper Il Sole 24 Ore on Tuesday.
Abertis shares closed 0.3 percent down on Tuesday at 16.30 euros, just below Atlantia's 16.5 euro offer for the stock. Atlantia closed 1.69 percent higher. ($1 = 0.9036 euros) (Additional reporting by Rodrigo de Miguel, Jesus Aguado in Madrid and Francesca Landini in Milan; Editing by Angus Berwick and David Evans)