I try to create a dynamic web project in eclipse and convert this project to a maven project. My project has this structure

src\main\java
src\main\resources
src\main\webapp
src\main\test
When i do Right click on the project > Configure > Convert to Maven Project, I get this error message :

Errors occurred during the build.
Errors running builder 'Maven Project Builder' on project 'Gestion'.
Could not calculate build plan: Plugin org.apache.maven.plugins:maven-war-plugin:2.3 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-war-plugin:jar:2.3
Plugin org.apache.maven.plugins:maven-war-plugin:2.3 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-war-plugin:jar:2.3
Could not calculate build plan: Plugin org.apache.maven.plugins:maven-war-plugin:2.3 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-war-plugin:jar:2.3
Plugin org.apache.maven.plugins:maven-war-plugin:2.3 or one of its dependencies could not be resolved: Failed to read artifact descriptor for o