U.S. President Barack Obama on Tuesday offered to assist Haiti after a strong earthquake hit the poor Caribbean country.

"My thoughts and prayers go out to those who have been affected by this earthquake. We are closely monitoring the situation and we stand ready to assist the people of Haiti," Obama said in a statement released by the White House.

After he was informed of the quake with a preliminary magnitude of 7.0 on Richter scale on Tuesday, the president asked his staff to make sure that embassy personnel are safe, and to begin preparations in the event that humanitarian assistance is needed.

The State Department, the United States Agency for International Development (USAID) and the United States Southern Command have begun working to coordinate an assessment and any such assistance.

Secretary of State Hillary Clinton said in Hawaii that her department is still gathering information about the condition on the ground in Haiti, but will do its part in providing assistance.

The quake struck at about 4:53 p.m. local time (2153 GMT), according to the U.S. Geological Survey (USGS).

The epicenter was just 15 km southwest of Haiti's capital Port-au-Prince, at a depth of 10 km.

The Pacific Tsunami Warning Center issued a local tsunami watch following the quake, but ruled out the possibility of a destructive widespread tsunami threat.