The EU emissions trading system (ETS) is facing a fresh challenge, this time from Australia­—an unexpected move by a country that also considers cap-and-trade systems a viable option to mitigate carbon dioxide emissions.

Australia was not involved in a meeting last year in Delhi and this year in Moscow that resulted in declarations of opposition to the ETS, but was one of 17 countries that met earlier this month in Washington to discuss ETS. Unlike the Delhi and Moscow meetings, the Washington meeting was convened to find a consensus approach to ETS rather than merely a statement of opposition.

But this weekend Australia’s House of Representatives passed a non-binding resolution calling on the Australian government to use all legal and diplomatic means to stop the application of ETS to international airlines. The resolution has the backing of both the conservative National Party of Australia and the ruling Labor Party.

The resolution, which has yet to be considered up by the upper house of the legislature, argues that either the International Air Transport Association or the International Civil Aviation Organization (ICAO) should broker any international deal on aviation’s role in climate change, says Bill Hemmings, program manager for aviation and shipping at the Brussels-based Transport & Environment advocacy group.

The opposition to Europe’s ETS comes as Australia considers its own legislation to establish a country-wide cap-and-trade system, a measure which has broad support, says Hemmings. Before the EU’s ETS applied to aviation, EU officials pointed to Australia’s plans for a cap-and-trade system as a possible equivalent measure that might be exempted from the ETS.

Countries or regions can apply to be exempted from the EU’s ETS if they have equivalent emissions-reduction measures in place.

Similar to legislation pending in the U.S. Senate, the resolution passed by Australia’s lower house objects to the EU charging for emissions for the entire length of a flight. This measure, and the participation in the Washington meetings, suggest that Australia’s stance is converging with that of the U.S. on climate change and aviation, environmental groups say.

This has been a disappointment to the environmental community. “Australia has been a constructive voice in ICAO,” says Pamela Campos, attorney for the Environmental Defense Fund. “We sincerely hope Australia will continue to be active as all eyes turn toward ICAO.”

ICAO has said it could have a proposal for market-based emissions-mitigation measures by the end of the year.