Facebook CEO Mark Zuckerberg and Microsoft co-founder Bill Gates have pledged to bring Internet access to everyone globally by 2020.

The pledge is part of an effort from the United Nations (UN) to eliminate poverty by 2030.

UN says just around half of the population globally have internet access, and expanding it further will enable women and girls to enhance their education and eradicate poverty.

The newly-signed declaration says, "When people have access to the tools and knowledge of the internet, they have access to opportunities that make life better for all of us.

"The internet belongs to everyone. It should be accessible by everyone."

The United Nations expects that it would cost between $3.5 and $5 trillion a year to meet its new global goals.

UN secretary-general Ban Ki-moon says over $25bn has already been committed, led by $3.3bn from the US. Canada, Germany and Sweden are also supporting the plans.

Zuckerberg wrote in a Facebook post, "If we connect the more than four billion people not yet online, we have a historic opportunity to lift the entire world in the coming decades."

Zuckerberg also announced that Facebook will work with the UN in bringing internet connectivity to refugee camps.