The United States is working with India to develop an investment platform to lower the cost of capital and increase private investment to fast-track India's energy transition, US Treasury Secretary Janet Yellen said on Monday.

After a bi-lateral meeting with India's finance minister Nirmala Sitharaman on the sidelines of a G20 meeting, Yellen said the two nations have been collaborating across a range of economic issues, including commercial and technological collaboration and strengthening supply chains.

"In particular, we look forward to working with India on an investment platform to deliver a lower cost of capital and increased private investment to speed India's energy transition," she said in a statement while attending the G20 in Gandhinagar, the capital of Gujarat, one of India's most industrialised states.

The visit is Yellen's third to India this year, indicating the growing closeness between the two countries.

"As we look ahead, we reaffirm our commitment to achieve substantial outcomes through close engagement," Sitharaman said in a statement, also noting the potential for development cooperation and alternate investment platforms for renewable energy.

The improvement in bilateral relations was highlighted during Prime Minister Narendra Modi's state visit to Washington last month which saw a slew of defence and high technology deals being signed.

Yellen also said the two countries are close to reaching an agreement on the global minimum tax system.

In a historical deal in 2021 pushed by the US nearly 140 countries agreed to a minimum 15% tax on large global firms along with additional 25% tax on "excess profits."

Australia and Japan are hoping to make progress during the G20 meeting on the global minimum tax.

Some analysts doubt whether an agreement can be reached for such a sweeping change in cross-border taxation, as some governments will want to give priority to national tax regimes.

Yellen will visit Vietnam after the G20 finance meetings end on July 18.