Two years ago, Kevin Rudd was elected Prime Minister of Australia on a platform that included a pledge to start legal action against Japan over its whaling in the Southern Ocean.

Since then, nothing has been lodged with the International Court of Justice.

Increasingly, Mr Rudd has found it difficult to respond to those who accuse him of being all talk and no action.

The visit to Australia of Japan's Foreign Minister, Katsuya Okada, who has spoken bullishly of retaining his country's whaling programme, placed him in a tight spot.

Mr Rudd's perhaps predictable response was to use the occasion to tell Japan to stop killing whales in the Southern Ocean by November, or Australia would take it to the international court.

Hopefully, the Prime Minister's threat was made largely to ward off domestic criticism.

If this were not the case, it spells ill for the fate of intense diplomatic efforts over the past few months to resolve the issue. Mr Rudd would be saying, in effect, that he had abandoned hope of their success.

The diplomacy has been described by his Government as "unprecedented", and hopes have been high that a breakthrough would be made within a few months.

Most logically, this would involve Japan abandoning or drastically scaling back its annual whaling in the Southern Ocean in exchange for a few carrots, including, perhaps, the resumption of commercial whaling in its own waters.

The diplomatic endeavours are clearly finely balanced. New Zealand Prime Minister John Key indicated as much when he suggested this week that the outcome of the diplomacy would be either a stunning success or a stunning failure.

This is an issue of considerable sensitivity to the new Japanese Government. It will not want to be seen to be bowing to international pressure over a matter that is seen as culturally important by many of Japan's elderly citizens.

The Key Government has not rushed to commit itself to backing any appeal to the International Court of Justice. This is a departure from its Labour predecessor, which would surely have not wished to be upstaged by Australia on such an emblematic issue.

But there is good reason for placing the strongest emphasis on diplomacy in the first instance. Legal action would, its advocates hope, lead to an immediate injunction requiring Japan to stop whaling until the case had been resolved.

But the court proceedings would drag on, probably for years. Diplomacy, if successful, would provide a far quicker solution.

There is also no certainty of incontrovertible success at the International Court of Justice. Australia has spent more than $1 million gathering video and photographic evidence against the Japanese whalers, including surveillance by one of its Customs vessels and from the air.

Nonetheless, both Australian and New Zealand authorities have cited "significant difficulties" in taking Japan to the court. Mr Rudd must also know that there is more mileage to be gained from a diplomacy, with a breakthrough ideally formulated in time for June's International Whaling Commission meeting in Hawaii.

The Australian Prime Minister is, however, gaining an unfortunate reputation for failing to deliver on key policies. His emissions trading scheme is bogged down, a roof insulation programme is revealing more problems by the day, and promises to take decisive action over the likes of ailing public hospitals and executive payouts have come to nought.

Perhaps he had little option but to talk tough in public to Mr Okada. The danger is that this will not have helped the diplomatic process. It, not resort to an international court or the over-the-top antics of protesters, offers the best chance of finally ending the cruel slaughter.