Sirleaf said that information sharing among member states had contributed immensely to the peace and security on the continent.
Sirleaf spoke to newsmen during her two-day official visit to the ECOWAS Commission in Abuja on Sunday.
She said that information sharing among member states had contributed immensely to the peace and security being enjoyed by member states.
"A lot of effort has been made to contain terrorist acts.
"The ECOWAS Commission has a very effective work in terms of the peace and security commission that has early warning signals.
"We all are still vulnerable to terrorist acts, but by the exchange of information and the effective work of the commission, we have been able to keep the peace, access where threats are and formulate proper measures to address them."
Sirleaf stated that her visit to the commission was aimed at familiarising herself with the structure, operations and staffing of the commission.
According to her, the sub-region has also moved in the direction of achieving the ECOWAS Vision 2020.
Sirleaf noted that the inclusion of Civil Society Organisations in ECOWAS programmes had contributed to development in the sub-region.
Speaking on the Economic Partnership Agreement, the ECOWAS Chairperson reiterated that the signing of the agreement would enhance sub-regional integration and trade.
She said efforts were being made to ensure the agreement was signed by all member states together.
She said: "Two member states still have concerns with signing of the EPA.
"We believe opening of markets, the preferential access that African countries will have (to European markets) will enable us broaden our economies and grow more.
"We will continue through the commission that has written a very good dossier on why we would affect our effort as trying to increase inter ECOWAS trade if we do not proceed with the agreement.
"A couple of our members states have already been granted access to the European markets.
"If we have our member states begin to open up their markets, this will take away from the efforts we have made as a union and from the harmonisation we have been able to achieve among ourselves."
She added that member states that had signed Memorandum of Understanding (MoU) with the European Union on the EPA had delayed implementation to allow all member states sign the agreement.
"Until the rest of our countries sign on, so we can all move together as one sub-region,’’ she said.
On her visit to Ghana, Sirleaf said that a code of conduct was signed by presidential candidates vying for elections on Dec. 7.
"They signed to maintain peace, ensure they work together, have their supporters commit to no violence and accept the results of the elections which reflects the wishes of the Ghanaian people," she said.
The ECOWAS Chairperson also held closed door meetings with the President of the commission, Mr Marcel de Souza, former President Olusegun Obasanjo and senior officials of the commission.