SOFIA, Feb 1 (Reuters) - Bulgaria has delayed the deadline for bids to run Sofia's airport for a fourth time to April 3, the transport ministry said on Friday, after potential bidders asked for more time.
The ministry has repeatedly offered extensions from the original Oct. 22 deadline for the 35-year concession.
The centre-right government relaunched the tender for Bulgaria's main air hub in July and wants to raise 550 million euros ($630 million) from the deal.
Opposition Socialists said the tender should be cancelled, saying a commitment not to build another state airport within 100 km (62 miles) and other elements might breach European Union rules. The government says it will clear details with the EU.
Britain's Manchester Airports Group (MAG) has said it plans to bid. India's GMR Group, Germany's Fraport have said they were looking at the tender. Spain's Aena is studying a joint bid with Australia's First State.
Others interested in the deal are France's Aeroports de Paris and Switzerland's Flughaven Zuerich.
$1 = 0.8730 euros Reporting by Tsvetelia Tsolova Editing by Edmund Blair