BRUSSELS — Even if it survives the next three months teetering on the brink of bankruptcy, Greece may have blown its best chance of a long-term debt deal by alienating its eurozone partners when it most needed their support.

Prime Minister Alexis Tsipras’s leftist-led government has so thoroughly shattered creditors’ trust that solutions that might have been on offer a few weeks ago now seem out of reach.

With a public debt equal to 175 percent of output and an economy struggling to pull out of a six-year depression, Athens needs all the good will it can summon. It owes 80 percent of that debt to official lenders after private bondholders took a hefty write-down in 2012.

Since outright debt forgiveness is politically impossible, the next-best solution would be for Greece to pay off its expensive I.M.F. loans early, redeem bonds held by the European Central Bank and extend the maturity of loans from eurozone governments to secure lower interest rates.