Doha will host a summit of major gas exporters, organisers of Gas Exporting Countries Forum say, as Western countries seek alternate supplies in the event of Russia invading Ukraine.
President Biden says he will notify US Congress about the designation that he says reflects "the importance of our relationship" with the Gulf country.
Doha emerges as saviour for post-Brexit Britain reeling under all-time high gas prices.
For many observers, the move indicates a lack of acceptance for Israel amongst several countries in the world.
Ex-Afghan leader Hamid Karzai says he invited the Taliban insurgents into the capital Kabul on August 15 so that "the city doesn't fall into chaos," following a covert departure of Ashraf Ghani and his team from the country.
Prince Mohammed's tour coincides with talks between Iran and world powers aimed at salvaging a 2015 nuclear pact, a deal Gulf Arab states have criticised for not tackling Tehran's missiles programme.
The agreements signed between the two countries included trade, investment, culture, sports, health and media sectors as Turkey's President Erdogan and Qatari Emir Al Thani move to expand relations.
Turkey's Foreign Minister Mevlut Cavusoglu and Qatari counterpart Sheikh Mohammed bin Abdulrahman al Thani discussed ways to keep Kabul airport open and deliver further aid to Afghanistan.
Turkey will sign more agreements with Qatar to further strengthen bilateral relations, says President Erdogan, ahead of his two-day visit to Qatar.
The visit will help lay the groundwork for further joint economic and strategic agreements between the two countries.
Efforts to stabilise Afghanistan have been undermined by international sanctions, with banks running out of cash and civil servants going unpaid.
A US interagency delegation flew to Doha for talks "focused on security and terrorism concerns and safe passage for US citizens, other foreign nationals and our Afghan partners," according to State Department spokesman.
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