Russia has invited troubled Greece to join the $100bn (£64.6bn, €89.6bn) Brics New Development Bank as its sixth member, as the European nation struggles with its debt payment to lenders including the International Monetary Fund (IMF).

The invitation was extended by Russian Deputy Finance Minister Sergey Storchak during a telephone conversation with Greek Prime Minister Alexis Tsipras, Greece's Syriza party said on its website.

Tsipras thanked Russia for the offer and said he would thoroughly examine the proposal. He will have a chance to discuss the invitation with the other Brics leaders during the upcoming International Economic Forum in St Petersburg.

The Brics nations – Brazil, Russia, India, China and South Africa – earlier decided to set up a $100bn bank and reserve fund to address emergency situations with similar paid-up capital. The bank will begin operations with a $50bn subscribed capital, divided equally between its member nations.

The bank is expected to rival other international financing agencies such as the IMF and the World Bank. Headquartered in Shanghai, the bank would finance infrastructure projects in the Brics nations and other developing nations. It is expected to begin operations by the end of 2015.

The invitation comes as Greece is struggling with its debt negotiations with creditors from the eurozone and the IMF, who had demanded austerity reforms, including pension cuts, privatisation and an end to collective bargaining, as necessary conditions for Greece to gain access to bailout funds.

Greece's finance minister Yanis Varoufakis said his country is in a liquidity crisis and it cannot move forward without the final €7.2bn tranche of the bailout funds.