As a security precaution, nearly all Amtrak passengers who want to ride the rails between Washington and Boston during the Republican National Convention (search) — Aug. 28 through Sept. 2 — will have to make reservations in advance, the railroad announced Monday.

Amtrak also warned of delays during the convention because of tighter security on all trains to and from New York's Pennsylvania Station (search), which is partly under the convention site, Madison Square Garden. Street access to that station will be limited to two entrances.

Trains will be searched before they leave in the morning, and police will conduct inspections while trains are en route. Bomb-sniffing dogs will be present on trains and at Penn Station, Amtrak said.

The only exception to the all-reservation rule will be weekend roundtrips on commuter trains between New York and Philadelphia and New York and Harrisburg, Pa.

Security officials at the Democratic National Convention now under way in Boston have closed the North Station rail terminal, which shares a building with the convention site. Rail commuters are bused in from a nearby city.