Ban was commenting on Assad’s speech on Sunday, in which he called for dialogue with opposition elements he deems acceptable, while vowing to stand fast against opponents he branded as foreign-backed "terrorists."
The speech has been widely condemned, with the United States calling it "detached from reality."
"The secretary-general was disappointed that the speech by President Bashar al-Assad on January 6 does not contribute to a solution that could end the terrible suffering of the Syrian people," said U.N. spokesman Martin Nesirky.
“The speech rejected the most important element of the Geneva Communique of 30 June 2012, namely a political transition and the establishment of a transitional governing body with full executive powers that would include representatives of all Syrians," Nesirky told reporters.
He said Ban "reaffirms his long-held view that there is no military solution to the conflict in Syria."
Ban and U.N.-Arab League envoy Lakhdar Brahimi are seeking a "political transition that includes the establishment of a transitional government and the holding of free and fair elections under the auspices of the United Nations," Nesirky added.
After the latest Assad rebuff of his peace efforts, Brahimi will hold talks on Wednesday with Iran's Foreign Minister Ali Akbar Salehi, whose country has been the only backer of Assad's address to the nation.
"What the Syrian people desperately need at this time are real solutions to the crisis that is tearing their nation apart," Ban said through his spokesman.
"The United Nations remains committed to do its utmost, in cooperation with other partners, to alleviate the suffering of the Syrian people inside and outside Syria," the spokesman said.
"The United Nations will also continue to help the people of Syria fulfill their legitimate aspirations for peace, dignity, freedom, justice and democracy in a united and sovereign Syria," he added.
Ban reaffirmed that there could not be a military solution to the 22-month-old war and added that it was "critically urgent" for the international community to help the Syrian people build a "new and democratic Syria."
The U.N. leader has shown exasperation at the U.N. Security Council's failure to agree on a position on Syria. Russia and China have vetoed three Western-proposed resolutions that would have threatened sanctions against Assad.
Brahimi is expected to brief the U.N. Security Council this month, the U.N. spokesman said. He is also trying to organize new talks with U.S. and Russian envoys in a bid to overcome differences on Syria.
The U.N. envoy was due to hold talks in Cairo on Monday with the prime minister and foreign minister of Qatar ahead of his meeting with Iran's foreign minister Wednesday. The U.N. had originally said the meeting with Salehi was on Tuesday.
The spokesman said he was unaware of any plan by Brahimi to return to Damascus.