The leaders of Botswana, Gabon, Chad and Tanzania made the statement at a gathering in London to discuss the illegal wildlife trade.

The aim is to draw up a global declaration that will tackle animal trafficking.

Prince Charles and The Duke of Cambridge are attending the meeting, hosted by the government.

The African leaders have said they will not act on an option to sell from their ivory stockpiles, in an effort to protect elephants.

Conservationists say poaching has reached a crisis point: tens of thousands of elephants, rhinos and tigers are being slaughtered each year.

The WWF estimates that the animal black market is worth $19bn (£12bn) a year.

The bulk of poaching takes place in Africa, but much of the demand comes from Asia, where animal products, such as rhino horns, are used in traditional medicine or are bought by the rich as trophies.

The UK's Foreign Secretary William Hague said that delegates at the meeting held at Lancaster House on Thursday would be adopting an "ambitious and powerful" London declaration.

This would include a commitment to renouncing the use of any products from species at threat of extinction and a promise to support the CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) ban on the international trade on ivory until elephant populations have stabilised.

He also said that poaching and trafficking should be treated as a serious crime, in the same category as drugs, arms and people trafficking.

He added: "The illegal wildlife trade is a global problem and it matters deeply to all of us gathered here today.

"We need to show the world our political commitment at the highest level across the globe to addressing this before it is to late."

In South Africa, 1,004 rhinos were killed in 2013, and across the whole continent it is estimated that more than 20,000 elephants were slaughtered for their tusks in 2012, according to the International Union for Conservation of Nature (IUCN).

The leaders of four African countries spoke at the start of the meeting.

The President of Gabon, Ali Bongo Ondimba, said: "Last year, we burnt an entire stockpile of ivory to show that Gabon has no tolerance for this."

He said his country had raised the minimum sentence for poaching to three years, and those found guilty of organised crime could be served with life in prison.

However, President Khama of Botswana said that he would put the country's ivory stockpiles out of reach of the markets.

As an additional pledge, the leaders of both African states, as well as the presidents of Chad and Tanzania, have agreed to a moratorium on the ivory trade for at least 10 years, as part of an elephant protection initiative.

While the trade of ivory has been banned under CITES since 1989, some states have been granted permission to sell their ivory stocks in the past.

In 1999, CITES authorised a "one-off" sale of stockpiled ivory from Zimbabwe, Botswana and Namibia to Japan, and in 2008 Namibia, Botswana, South Africa and Zimbabwe sold their stocks to buyers in China and Japan.

In essence, by issuing a 10-year moratorium, the four African states are saying they will uphold the ban, and not ask for permission from CITES to sell any of their ivory.

Some organisations believe the CITES-sanctioned sales have been the driver for the current rise in demand for ivory, and want to have all ivory sales banned and stockpiles destroyed.

Mary Rice, executive director of the Environmental Investigation Agency, said: "We need to learn from history and permanently shut down all ivory trade - international and domestic."

Delegates from Asia, including those from China and Vietnam where the demand is greatest, did not speak at the opening of the meeting.

Interpol, the international intelligence agency, which will also be present at the meeting, says most of this being driven by organised crime syndicates, who have moved from narcotics and guns onto wildlife.

At a symposium held at the Zoological Society of London on Tuesday and Wednesday, conservationists said the problem needed to be tackled on several different fronts.

They said improved legislation was needed, rangers needed support on the ground and the growing demand had to be tackled with education and marketing campaigns.

Heather Sohl, chief adviser on species for WWF-UK, said: "What we really want to see is these world leaders coming together and agreeing strong action for tackling illegal wildlife trafficking, looking at improving law enforcement and criminal justice, reducing the demand for illegal wildlife products, and ensuring sustainable livelihood's for communities affected by the trade.

"We need to have strong action and for those people to take that home to their governments and make sure it is implemented at a scale and urgency that is commensurate for the problems we are seeing."