Washington, Apr 27 (IANS/EFE): US President Barack Obama promised Friday an in-depth investigation into the possible use of chemical weapons in Syria, and said if that proves to be the case, it will change his "calculus" about how to deal with the crisis in the Middle Eastern country.

Use of chemical weapons in Syria would bring "increased urgency to what is already a significant security problem and humanitarian problem in the region", Obama said in a brief joint press appearance with visiting Jordanian King Abdullah II.

The president maintained the same prudence as other White House officials, who have insisted that intelligence on the use of chemical weapons in Syria is not yet sufficient and, therefore, credible and confirmed incidents of their use must be identified before any decisions are taken.

US intelligence has concluded with "varying degrees of confidence" that chemical weapons have been used in Syria by the regime of President Bashar al-Assad, Defense Secretary Chuck Hagel said Thursday during a visit to the United Arab Emirates.

Obama has said clearly for some time that the use of such weapons or their transferral to terrorist groups would be crossing a "red line".

Up to now the US has been providing "non-lethal" assistance to Syrian opposition groups and is holding back on giving them arms for fear they could fall into the hands of terrorist organizations.

Some elements of the Syrian opposition have ties to Al Qaeda and other extremist groups.

The conflict in Syria broke out in March 2011 and has caused the death of more than 70,000 people plus an exodus of more than 2 million displaced persons, according to a UN report.