A change of government late last year has raised hopes that authorities might move more quickly with the cleanup and reconstruction.
Since taking office in late December, Abe has made a point of frequently visiting the disaster zone, promising faster action and plans to raise the long-term reconstruction budget to 25 trillion yen ($262 billion) from 19 trillion yen (about $200 billion).
"We cannot turn away from the harsh reality of the affected areas. The Great East Japan Earthquake still is an ongoing event," Abe said at the memorial gathering in Tokyo. "Many of those hit by the disaster are still facing uncertainty over their futures."
The struggles to rebuild and to cope with the nuclear disaster are only the most immediate issues Japan is grappling with as it searches for new drivers for growth as its export manufacturing lags, its society ages and its huge national debt grows ever bigger.
Those broader issues are also hindering the reconstruction. Towns want to rebuild, but they face the stark reality of dwindling, aging populations that are shrinking further as residents give up on ever finding new jobs. The tsunami and nuclear crisis devastated local fish processing and tourism industries, accelerating a decline that began decades before.
Meanwhile, the costly decommissioning the Fukushima Dai-ichi nuclear plant could take 40 years as its operator works on finding and removing melted nuclear fuel from inside, disposing the spent fuel rods and treating the many tons of contaminated wastewater used to cool the reactors.
Following the Fukushima disaster, Japan's 50 still viable nuclear reactors were shut down for regular inspections and then for special tests to check their disaster preparedness. Two were restarted last summer to help meet power shortages, but most Japanese remain opposed to restarting more plants.
The government, though, looks likely to back away from a decision to phase out nuclear power by the 2030s. Abe says it may take a decade to decide on what Japan's energy mix should be.
Associated Press writers Malcolm Foster and Mari Yamaguchi in Tokyo and Emily Wang in Kesennuma, Japan, contributed to this report.