For politicians, handshakes are not only great photo opportunities but they are also relatively easy. The tough part of the deal they have shaken on, is making it happen.

For the presidents of Sudan and South Sudan the challenge is particularly daunting.

Sudanese leader Omar Al-Bashir shook hands the other day with his South Sudanese opposite number, Salva Kiir in the Ethiopian capital Addis Ababa.

The gesture came at the end of a meeting between the two men, held on the fringe of the African Union summit, which both were attending. Because no details were immediately given about the nature and tenor of the talks, it was not possible to know if the presidents were celebrating a deal or felt that a handshake was the least they could manage in the face of a growing humanitarian as well as political crisis.

Both leaders are under a lot of pressure to reach agreement over the key issues of border delineation, the transport of oil through Sudan from fields predominantly in South Sudan and the division of the national debt.

None of this was resolved when, a year ago this month, South Sudan became an independent state, after half a century of fighting the north, followed by six years of coalition government, in which southern leaders could not be convinced to maintain a single Sudan. Exercising a right under the 2005 peace treaty, a referendum in the south showed voters overwhelmingly choosing partition.

However, almost from the outset, the military on both sides were at odds over the ownership of border towns and fighting flared. The confrontations were compounded by inter-tribal rivalries. As a result of the instability and breakdown in markets and food supplies, tens of thousands of refugees fled deeper into South Sudan.

International charities are now reporting a rising humanitarian crisis in temporary camps that simply cannot cope with the influx of refugees. Many of the arrivals are in a pitiful state, having found little to eat on their flight except roots. With diseases now breaking out in the camps, undernourished children, in particular, are highly vulnerable to deadly infections.

Unfortunately in the past, similar devastating consequences have occurred for civilians without political leaders taking decisive action to stop them. Nevertheless, the human cost of political failure is likely to bring the international community to exert strong pressure on both sides to find a lasting deal.

There is however an added complexity. In the break-up of Sudan, resource-hungry China has followed the oil, most of which sits beneath South Sudan.

It is also helping the South Sudanese build a new state from scratch.

Beijing is reportedly willing to fund an export pipeline south through Kenya. This plan may have emboldened Kiir to drive a harder bargain with Bashir. It must be hoped however that the Chinese are not thinking solely in terms of crude supplies but have a wider agenda. They know the Bashir administration well and are also in a position to influence the South Sudanese. They should use that knowledge and leverage to promote an enduring settlement between the two countries.