The World Bank on Monday said it is looking at ways to expand the guarantees it provides for commercial loans to boost the private financing available to developing countries.

Some emerging economies have been unable to tap international markets as global interest rates soar and with uncertainty about when the U.S. Federal Reserve will reach the end of its current tightening cycle.

A recent selloff in U.S. Treasuries pushed yields on 10-year notes to a 16-year high, in turn lifting borrowing costs for developing economies.

"We are looking very systematically at how we can expand our work with the private sector. And that includes many forms of guarantees," World Bank Senior Managing Director Axel van Trotsenburg told Reuters on the sidelines of the World Bank and International Monetary Fund annual meetings in Marrakech.

One of the biggest challenges, Van Trotsenburg said, is how to provide more funding for climate change initiatives.

"The financing falls short and governments do not have the firepower to do that. So we need to complement intelligently with the private sector," he added.

Van Trotsenburg did not provide any figures nor a timeframe. World Bank guarantees have mobilised more than $42 billion in commercial capital and private investment spanning energy projects to sovereign financing in the last two decades, according to its website.

The multilateral lender has already provided partial guarantees for sovereign bonds through its International Development Association (IDA), including for a $1 billion Eurobond issue by Ghana in 2015.

U.S. Treasury Secretary Janet Yellen in April said the bank must take steps to allow its private sector and poor country lending arms to lend to sub-sovereign entities such as cities and regional authorities.

The bank is currently pressing for more grants and new capital from member countries, even as it leverages its balance sheet to scale up lending for responses to climate change and other global crises.

(Reporting by Jorgelina do Rosario; Editing by Kirsten Donovan)