U.S. Education Secretary Arne Duncan urged city and state officials Tuesday to resolve the Philadelphia School District's $304 million shortfall to avert a crisis in the city's schools.

"There's no excuse for a public school system anywhere in the U.S. to be in this situation in the 21st century, and it's even worse to see it in Philadelphia, the cornerstone of this great country and the cradle for our founding principles," Duncan said in a statement released late Tuesday. "I strongly urge everyone involved to continue working together to avert this educational crisis."

Duncan said his continued outreach to Gov. Corbett, Mayor Nutter, Superintendent William R. Hite Jr., and Jerry Jordan, president of the Philadelphia Federation of Teachers, "assures me that fixing this is their number-one priority."

The nation's top education official said he had instructed his staff to provide "any needed technical assistance to both the district and the commonwealth." He added: "Without courage and leadership, I worry greatly that Philadelphia's children will be shortchanged. We must invest in public education, not abandon it."

Duncan spoke a day after Randi Weingarten, president of the American Federation of Teachers, and Diane Ravitch, a national education expert, revealed that they had appealed to him to help Philadelphia schools.

In a Friday letter made public early Monday, Weingarten and Ravitch wrote to wrote Duncan: "We are writing to ask for your urgent intervention to preserve public education for the children of Philadelphia."

District spokesman Fernando Gallard said Tuesday night that in an earlier phone coversation with Duncan, Hite expressed his commitment to continue working with all parties to "bring forward a resolution that benefits the students in the School District of Philadelphia."

Gallard said Hite also said he was still working with labor on finding savings.

The calls for action come as the district awaits word on the fate of final legislation required to put in place the $140 million package of city and state funds that Gov. Corbett announced Sunday to help city schools.

The plan includes a projected $30 million from improved city tax collections, $15.7 million in additional basic-education funds from the state, and a $45 million one-time state grant.

The governor also backs extension of Philadelphia's extra 1 percent sales tax, which was set to expire next June. An extension would let the city borrow $50 million against future collections of that tax. Starting next July, the extended tax also would generate $120 million a year for the district.

The state House approved the $45 million in aid and the extension of the 1 percent city sales tax Monday night. Those measures still need final approval by the Senate.

Meanwhile, the Committee of Seventy was scheduled to announce Wednesday that it would urge City Council to hold an unusual summer session "as soon as possible" to deal with school funding.

The nonpartisan committee called on Council to work with Nutter "to guarantee the city's portion of funding for the struggling Philadelphia public schools, most likely through budget cuts."

Council approved a budget this spring to provide an additional $75 million for schools: $28 million in future property-tax collections and $45 million from a new $2-per-pack cigarette tax in the city. The legislature did not pass the cigarette tax.

"It's up to Mayor Nutter and City Council to take control of this crisis immediately and avoid a calamity," said Zack Stalberg, president and chief executive of the committee.