The world’s second and third largest issuers of environmentally friendly “green bonds” are moving hand in hand to unify market standards for the financial instrument.

Officials from China and European countries — as well as those from Japan, Canada and India — are scheduled to meet in Brussels on March 21 to discuss efforts to unify definitions and standards for the fledgling green finance market, according to Sean Kidney, CEO of non-governmental organization the Climate Bonds Initiative (CBI), which focuses on promoting investment in projects that contribute to addressing climate change.

Green bonds are fixed-income financial instruments targeted in some way toward climate and environmental projects.

A total of $167 billion-worth of such bonds was issued in 2018, according to CBI. However, global standards for their investment and supervision are essentially non-existent, and each country follows its own rules.

Related: For Bond Investors in China, It’s Not Easy Buying Green

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