ATHENS, Greece -- International Olympic Committee officials again urged organizers of the 2004 Athens Games to overcome construction delays.

IOC officials completed a two-day review and put organizers and the government on notice that the IOC will be "pretty tough'' to ensure contracts get signed and construction crews start working on all sports venues.

"The delays are there,'' Denis Oswald, chairman of the IOC review team, said Thursday. "Contracts which were supposed to be signed are not signed ... and the delays are about on an average of 50 days more or less, and this is, of course, a concern.''

Delays have been the bane of Athens' preparations since it was first awarded the Olympics in 1997. The problem grew so serious that former IOC President Juan Antonio Samaranch warned in 2000 that the Athens Games were in danger.

Athens has since made up for most of the lost time, but both IOC officials and Athens organizers worry that just over two years remains before the opening ceremony.

"There are times when the size and the time that is running scares us. But when everyday we see what we are building rising higher and higher, we know it is worth it,'' said Athens 2004 head Gianna Angelopoulos-Daskalaki.

Some projects are ahead of schedule, according to Angelopoulos-Daskalaki. They include the Olympic Village, a number of sports venues and the main press and broadcasting centers.

Most of the problems focus on Athens' old international airport in the seaside suburb of Hellenikon -- slated to be a main hub for a number of Olympic sports. Planned venues include an artificial whitewater course for canoe and kayak, basketball arenas and baseball diamonds.

Delays have already forced organizers to shrink the whitewater facility.

IOC officials said they had been assured during an April inspection visit that contracts would be signed for Hellenikon before their current review.

"The Hellenikon situation is one example. At our last visit we could not fully assess the situation because a number of contracts were supposed to be signed after our visit ... They were planned to be signed in April or May,'' Oswald said. "Now we are at the end of June and these contracts have not been signed for legal reasons and therefore we say danger.''

Another trouble spot at Hellenikon is a legal dispute over whether to give private pilots continued use of a runway -- which was supposed to be torn up months ago.

"Time is the most precious thing we have at our disposal and what is precious normally is rare ... we have to be pretty tough in monitoring this remaining time,'' Oswald said.

Another unexpected delay arose over the cancellation of a contract to refurbish the Karaiskaki stadium, site of the soccer finals.

"We certainly did not expect the new situation regarding Karaiskaki,'' Oswald said, adding that "it is now doubtful that Karaiskaki stadium will be available to used for the football tournament.''

Other problem areas include the modern pentathlon, badminton and tennis venues, where test events had to be pushed back to allow for construction.

IOC officials also stressed the government must complete a number of highway projects designed to alleviate traffic congestion in a city of 5 million people and 2 million cars.