China's foreign minister is to arrive in South Sudan - the first high-level visit since independence in July.Yang Jiechi is expected to urge the government in Juba to develop a better relationship with Sudan.Mr Yang expressed similar views during his talks with Sudanese President Omar al-Bashir earlier this week.China - which is heavily involved in Sudanese oil extraction - has been a strong supporter of Mr Bashir, despite claims of Sudan's war crimes in Darfur.'Urgent solutions'Mr Yang's visit comes one month to the day after South Sudan became independent.Beijing's links to Khartoum have been strong in recent years, but the Chinese have made an effort to improve their ties with Juba too, the BBC's James Copnall in Khartoum reports.Last year, Sudan as a whole was the sixth largest source of oil imports of China, and now three-quarters of that oil belongs to South Sudan, our correspondent says.However, South Sudan has to export oil via the north because it has no port or refineries of its own. The two sides have so far failed to agree on transit fees, or how to share oil revenue.The visit comes after Sudan last week released a cargo of South Sudanese oil it had blocked in a row over custom duties.During his two-day visit to Khartoum which ended on Monday, Mr Yang urged both the north and the south to find "urgent solutions" to their outstanding differences for the sake of stability."We hope that Sudan and South Sudan will have good neighbourly relations based on the exchange of benefits," he said.Relations between the two states remain tense.South Sudan's independence follows decades of north-south conflict.