Japan should shore up its nuclear safety credibility and prime its economy to bounce back from the quake-tsunami disaster, a US task force said Thursday.

A team from the Center for Strategic and International Studies (CSIS) think-tank spent much of the last six months in Japan observing the aftermath of the March 11 natural disaster and subsequent nuclear crisis, then issued a report offering key recommendations on disaster preparedness, economics, health, nuclear energy and civil society.

Among the most urgent was the call for an independent, international study of Japan's low-dose, long-term radiation problem and how to resolve "outstanding safety issues" sparked by the fuel meltdown at the Fukushima plant.

It also called for improved communication methods and improved steps towards maintaining the population's health in the face of a future crisis.

Anxiety about radiation exposure, the report said, "stems from inconsistent safety standards, confusing communications, a lack of adequate preparedness programs, public admissions by the Japanese government that data was withheld at points in the crisis, the discovery of multiple inland hot spots' far from the coastal nuclear plants, and a revised estimate showing that the radiation released was twice what had originally been acknowledged."

"We think that there is a serious trust and credibility problem," said Stephen Morrison, leader of the task force's health working group.

Morrison said at a briefing marking the report's release that an independent entity "could greatly advance our knowledge on those key areas where I said we do not have answers at hand today."

On the economic front, the report stressed that the disaster "illuminated several challenges Japan was already facing, such as deflation, an aging society, and massive public debt," and said the country must now urgently address the "difficult balancing act" between stimulus and debt reduction.

The report recommended an ambitious trade liberalization agenda, reducing corporate and individual tax rates and adjusting the consumption tax rate to alleviate fiscal pressures compounded by the crisis, which CSIS estimated caused at least $220 billion in loss of infrastructure and assets.

"Japan can still benefit enormously from opening up and engaging the global trading system, and I hope that next week we will see that," said economic recovery working group leader Tim Adams, referring to trade and business talks set for the upcoming Asia-Pacific Economic Cooperation forum in Hawaii.

He also recommended Japan set up key special economic zones with a series of incentives to drive foreign and domestic capital to the quake-hit region.

US Deputy Secretary of State Thomas Nides said Washington would be there for Japan through the rebuilding and beyond.

"We do not want just to put things back the way they were; we want to rebuild for the future, and for the next generation," Nides told the gathering at CSIS.

"One of the best ways that we can do that is by spreading the message that Japan is open for business."

This year's disaster in Japan left more than 20,000 people dead or missing and thousands more homeless, triggered the worst nuclear crisis in decades, crippled several industries, and left many foreign firms hesitant to invest in the country.