The Foreign Secretary said the events in Egypt – as well as other countries across the region – would echo for decades and, while there would be “setbacks”, it was important to be optimistic about the desires of the majority of people for peaceful democracy.
Mr Hague said Britain and international partners could influence events in Egypt, highlighting discussions over aid and revocation of some export licences.
But the senior Tory Minister said it was vital for him to deal with the government in Egypt as it was today, even though it came to power earlier in the summer as a result of military intervention.
Speaking on the BBC Radio 4 Today, Mr Hague said: “It is a very bleak situation (in Egypt), it is hard to under-estimate the hate and distrust on both sides of the politics in Egypt.
“But I would not accept... there is nothing at all we can do about it. Our influence may be limited – it is a proudly independent country – and there may be years of turbulence in Egypt and other countries going through this profound debate about the nature of democracy and the role of religion in their society.
“We have to do our best to promote democratic institutions and political dialogue and to keep faith with the majority of Egyptians who just want a peaceful and stable country.”
And the Foreign Secretary added: “What is happening now in the Middle East is the most important event so far of the 21st century, even compared to the financial crisis we have been through and its impact on world affairs. “
Mr Hague spoke out as European Union ambassadors prepared for a meeting to discuss the crisis in Egypt amid international alarm as the death toll soared to 1,000 in just five days as the interim military government cracks down on the supporters of ousted Islamic president Mohammed Morsi.