After days of brinksmanship, high-stakes political diplomacy and hard work, leaders of the state and City and County of Honolulu reached agreement yesterday on a plan that one day might bring a new era of transportation to O'ahu.

But for all the jubilation yesterday, announced at a state Capitol courtyard news conference attended by a group of clearly satisfied construction workers, there are miles to go — both literally and politically — before Honolulu has a viable transit alternative.

What was rescued yesterday was a plan that allows the counties to raise a half-percentage-point excise tax for a minimum of 15 years to help pay for transit alternatives. It's estimated the tax would be worth $150 million a year for Honolulu.

Gov. Linda Lingle had threatened to veto the plan on the grounds it violated her strong home-rule inclination because the state would impose, collect and then pass on the tax.

She was also unhappy that lawmakers chose to take a full 10 percent of the tax for state purposes — an amount far in excess of what would be needed to administer the tax.

After a hectic series of meetings among legislators, the governor and her staff and the mayor and his staff, a compromise was reached. House Speaker Calvin Say and Senate President Robert Bunda promised, in writing, to take up Lingle's concerns when the Legislature convenes next year.

The law does not take effect until January 2007 in any event.

The details of how Honolulu would impose and collect the tax will be worked out in the coming months.

Also to be discussed is that 10 percent set-aside, which Say said was never part of the Legislature's financial plan and thus is back on the table for negotiation.

So, what is on track now is a funding mechanism for a transit start (an incomplete mechanism by any measure since the county's original proposal was for a full 1 percentage-point excise tax hike).

Still to be determined are core questions of what technology (what kind of system, from train to light rail to even elevated busways) will be best for O'ahu and where system routes will be built.

Mayor Mufi Hannemann acknowledged yesterday that the tax money, plus whatever Washington throws into the pot, will be enough to start a system but not enough to finish it.

So, what happened yesterday was a historic, but still tentative, step forward in Honolulu's decades-old quest for a transit alternative that will meet the needs of its people and its economy.