By Isabel Reynolds

TOKYO, June 4 (Reuters) - Japanese Prime Minister Shinzo Abe will be playing to a domestic audience at this week's G8 summit, desperate to lift his popularity ratings off record lows ahead of his first big ballot-box test since taking office.

A lacklustre performance could worsen the already bleak prospects for Abe's Liberal Democratic Party (LDP) in July's upper house election.

The loss of a majority in the upper house would not force Abe to resign, but it might tempt the LDP to replace a faltering leader once touted as their popular young "prince".

U.S. President George W. Bush's proposal for a global climate change strategy last week may have scuppered Abe's chance to take the initiative on global warming in his first appearance at the G8 forum, which opens on Thursday.

His signature diplomatic issue -- the return of Japanese citizens abducted by North Korea in the 1970s and 1980s -- has fallen from the media spotlight, with no clear progress since five surviving victims were returned in 2002.

Talks aimed at stopping Pyongyang's nuclear programme are also stalled, making it hard for him to shine.

But some analysts say the lack of a clear role at G8 matters less than the chance to make plenty of media appearances in the company of other world leaders.

"It has been a tradition for Japanese cabinets to use diplomacy and television 'performance' abroad to pull up their support ratings," said political commentator Minoru Morita.

"I think they will succeed to a limited extent, because G8 is more about appearances than actual content. But it will be a temporary effect."

Abe's popularity has been hammered by the suicide of a minister who faced questioning in parliament over links to political funding scandals, and by a huge pension system bungle.

In the latest media survey to underscore his woes, a weekend poll by the Asahi newspaper showed approval for Abe's cabinet had slid to 30 percent, down from 36 percent a week earlier and the lowest since he took office in September.

DIPLOMATIC BOOST

Abe's support was buoyed early on by his ice-breaking visits to China and South Korea at which he thawed ties chilled by his predecessor Junichiro Koizumi's visits to a war shrine seen by many in Asia as a symbol of Japan's militarism.

His popularity also jumped after a summit with Bush in April -- so his advisers could be looking to repeat the effect.

"As long as nothing goes drastically wrong, there is a tendency for support to rise while a leader is abroad," said political analyst Takashi Kiuchi.

"But this is going to be a hard summit for scoring points. I don't see him producing any positive surprises."

No bilateral meeting has been fixed between Bush and Abe in Germany, in what some domestic newspapers said was a blow to the Japanese leader's hopes of boosting his profile.

Still, the trip will likely come as a welcome respite from the drumbeat of media coverage of Abe's domestic headaches.

"The electorate is gradually backing away from the Abe administration," Morita said. "G8 may improve things slightly, but it is highly likely his popularity ratings will tumble right down again before the election on July 22."

Some commentators say Abe is likely on the way out, with his outspoken Foreign Minister, Taro Aso, the frontrunner to take over. But the powerful ruling party may still be able to salvage the situation before the poll, others say. (Additional reporting by Elaine Lies)

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