Adding more highway capacity, improving freight mobility and building more mass transit are crucial to the future of Pierce, King and Snohomish counties. These are truly urgent regional priorities.

Yet now Pierce County Executive John Ladenburg is threatening to oppose the two-part package if part of the Pierce County’s cross-base highway is dropped from the roads piece. How can that be?

A monumental difference on strategy, it turns out, has developed between Ladenburg and Regional Transportation Improvement District leaders such as County Councilman Shawn Bunney on the massive regional transportation funding package.

This difference must be resolved soon if years of hard work on transportation solutions are to pay off.

Ladenburg is chairman of Sound Transit, which has spent more than two years developing a $10.8 billion proposal to build Phase II of the system, which would include extending light rail to Tacoma. Bunney is co-chair of the RTID, the body created by the Legislature to plan a highway-construction proposal for the same November ballot. RTID leaders envision an $8.7 billion proposal for regional road and bridge work.

The Legislature yoked the two measures; both must win voter approval if either is to pass.

Until recently, the roads plan was to include construction of the long-planned cross-base highway linking east-to-west the Federickson industrial area with Interstate 5 in Lakewood. The highway is considered key to more economic development at Frederickson and another way for frustrated South Pierce County commuters to reach Interstate 5 and points north. This newspaper has long backed the project.

But Bunney and other RTID leaders are convinced that environmental opposition to the cross-base highway could be enough to sink both measures at the polls. Bunney backs cross-base, but he argues it’s not worth risking defeat of both ballot measures.

Instead, he proposes to divert $50 million now allocated for the highway between Fort Lewis and McChord Air Force base to help widen 176th Street East and Canyon Road. The new plan would still build new interchanges in Lakewood and make other improvements that constitute 60 percent of the cost of the cross-base highway project. Postpone the fight over completing the highway, Bunney advises.

Ladenburg disagrees. County Council members are divided.

This amounts to a giant poker game with exceedingly high stakes. Would environmentalists really try to kill expanded mass transit in three counties just to stop the cross-base project? Can backers of the roads package, which includes some huge King County projects and extension of Highway 167 from Puyallup to Fife, afford to take the chance?

We’re not prepared to endorse either alternative at this point. Both Ladenburg and Bunney want what’s best for Pierce County, and both make good arguments. So far this appears to be an honest difference of opinion rather than a personal or political dispute, and that’s good.

But a hard-won consensus on Pierce County’s top highway priorities has suddenly fractured. It needs to be repaired soon. The final RTID package is to be decided next month. It’s time for an honest and informed assessment of political realities and perhaps for painful decisions. The stakes are too high to do anything else.