The head of the United Nations said Tuesday that the world body is "taking the lead now" on international efforts to fight the Ebola outbreak in West Africa that has killed some 2,400 people and could spread further.

Secretary-General Ban Ki-moon said at a press briefing that the UN General Assembly next week will follow-up with a high-level meeting -- the disease, he said, taking on "a special focus" at an event that will welcome more than 140 heads of state and government. Before that, an emergency meeting will be held Thursday in which Ban and World Health Organization director general Margaret Chan plan to "outline the international action plan to contain this threat."

The UN's response so far has drawn criticism, with the president of France-based humanitarian group Doctors Without Borders on Tuesday calling it "dangerously behind."

Ban also said the disease could "affect political instability" if it isn't "properly contained and properly treated."

"This is not just a health crisis," Ban told reporters. "It has grave humanitarian, economic and social consequences that could spread far beyond the affected countries."

West Africa's Liberia, Sierra Leone and Guinea have been hardest hit by Ebola, which also has reached Nigeria and Senegal. Ebola is spread through direct contact with the bodily fluids of sick patients, making doctors and nurses especially vulnerable to contracting the virus, which has no vaccine or approved treatment.

In his role as UN chief, Ban also said he has discussed the outbreak with President Barack Obama, along with leaders from the U.K., France, Italy, the European Union and Cuba. He added that he has urged leaders in the most affected countries to establish special centres that aim to isolate infected people from non-infected relatives in an effort to stem the spread of Ebola.

Many regional and major airlines in August suspended services to Liberia, Sierra Leone and Guinea, complicating efforts to bring medical workers and supplies to the region.

In the briefing, Ban reiterated an appealed for international airlines and shipping companies not to suspend services to countries affected by Ebola. Doing so, he said, hampers and prevents the UN and international health workers from providing humanitarian and medical assistance.