The Pine Tree and Granite states are divided in part by the Piscataqua River and, more to the point, by governing philosophies on tax and spending issues that come from different spots on the political spectrum.

But the river and the governing fiscal paradigms are linked at the cross-border communities of Kittery and Portsmouth, N.H., where two bridges spanning the Piscataqua are in serious need of repair or replacement, and maintenance issues continue to be unresolved for a third one.

The need to replace the Memorial Bridge, which links the two communities’ downtowns and also offers the only bicycle and pedestrian paths across the river, seems obvious. Two months ago a rusted portion fell off into the river, and the bridge is growing more hazardous by the day.

Also up for substantial repair or replacement is the Sarah Mildred Long Bridge, which includes a rail line serving the Portsmouth Naval Shipyard, an industrial site employing 4,200 workers that, despite its name, is on the Maine side of the border.

And then there’s the high-level Piscataqua Bridge, which carries I-95 traffic and has its own maintenance requirements. New Hampshire has pushed for action on the bridges’ needs for some time, seeking to keep or replace both the Memorial and Long bridges.

Maine, on the other hand, had indicated it might be unwilling to replace the former one, a decision that, no matter how stressed the state’s highway fund is, seemed shortsighted.

However, after a bid for stimulus funding for the bridges was turned down, both states’ governors signed an agreement this week to form a task force to explore ways to finance the $300 million it is estimated to cost to upgrade both bridges.

Maine’s commitment to that goal is worth praise, but it shouldn’t have taken this long to get there. Part of the problem of delaying repairs of such vital pieces of transportation infrastructure is that what can be done at low cost if it’s done early can be very expensive after years have passed.

Cross-river traffic benefits both communities and both states. Letting a structure disappear that is both a symbol and a facilitator of those benefits would be bad for commerce — and for comity between mutually dependant neighbors.