WARSAW (Reuters) - Spain and Croatia fans heading for the Euro 2012 Group C clash on Monday may find the main road to Gdansk's PGE Arena blocked by up to 60 bulldozers and diggers because of a protest over payments due to sub-contractors.

Local authorities stress they will provide alternative routes for trams and buses to the match, which kicks off at 2045 local time (1845 GMT), but that may not help foreign car drivers following GPS-recommended routes to the stadium.

Slowackiego Avenue is the main road linking Gdansk airport with the amber-shaped arena, also due to host Germany's quarter-final against Greece next week.

The sub-contractors say they have not been paid for the construction of the road.

"Due to the blockade we have worked out a different plan for public transport to the stadium. Access to the stadium will be ensured," the Gdansk Transport Authority told leading Polish website Gazeta.pl, urging fans to travel by bus, tram or train.

Poland has worked hard to try to get its road, hotel and stadium infrastructure ready for the tournament it is co-hosting with Ukraine, but the final push has left a number of leading builders bankrupt or heading for insolvency.

Up to 100 contractors are seeking about 50 million zlotys ($15 million) for their work on the Gdansk road from general contractor Hydrobudowa, part of the debt-laden PBG group.

PBG, which has been granted bankruptcy protection, is the biggest Polish builder to falter in the wake of the 20 billion euro spending spree ahead of the tournament.

The company helped build three of the country's four Euro 2012 stadiums. ($1 = 3.3912 Polish zlotys)