Environmental, social and governance (ESG) fund assets have grown from $10 billion in 2015 to $246 billion in March 2021, she said.

Yellen urged global partners to "unlock progress towards greater ESG clarity and transparency so these investments can play a key role in closing the infrastructure gap and lowering global emissions."

"Poor quality or availability of ESG data and lack of standardized ESG metrics are often cited as barriers to further deployment of sustainable finance," she said, addressing a meeting of G20 member states convened to discuss infrastructure investment.

She said a lack of clear measurement could lead to "green washing," the practice of exaggerating environmental and emissions measures to appear more climate friendly and attract investors.

Yellen added that the G20 was not only working to develop indicators that incorporate ESG considerations but also "resilience and life cycle cost."

Sustainability-linked debt issuances "have grown at an annualized rate of 60 percent over the last eight years," Yellen said, deeming it essential to "do more."

"In order to mobilize additional investments into clean infrastructure, investors are demanding clear and comparable ESG data and metrics," she said.

"There are legitimate concerns over their potential impact on investment and project costs," Yellen acknowledged.

But she said the Treasury Department would "work with international partners to identify and address barriers to emerging market infrastructure investments."

According to Washington, a shortfall of $2.5 to $3 billion per year in financing infrastructure exists at the global level, a gap which it says cannot be bridged by the public sector alone and requires private investment.

Yellen already insisted that private investors will have to step up to finance renewable energy and other innovations for the US economy during a virtual summit hosted by US President Joe Biden in April, which brought together approximately 40 world leaders.