Washingtonians, prepare for traffic gridlock early next week as the city battens down for an international nuclear security summit that will lock down blocks of downtown, close a Metro station and tie up traffic with multiple motorcades.

The summit is slated to attract more than 40 world leaders to the Walter E. Washington Convention Center on Monday and Tuesday, but the shutdowns begin Sunday evening, and some will last until Wednesday morning. Parking could be fouled up as early as Friday, officials warn.