RUSUTSU, Japan — A declaration by the Group of Eight industrial countries that endorses a halving of the world's emissions of greenhouse gases by 2050 was heralded by Canada on Tuesday as an "an empty slogan."

Prime Minister Stephen Harper said the strength of the G8 statement was getting Russia and the United States - the two holdouts on long-term carbon cuts at last year's G8 summit - to change their tune this time around while China and India go their own way.

"This is the first time either of those countries have conceded the necessity of having a long-term, mandatory goal for reduction," he said in an interview.

"There's also now a firm recognition of all countries that to make these objectives effective, like we did with our aid to Africa, we have got to have mandatory participation by all major economies, by all major emitters, spitters and bullshitters."