Iraqi President Jalal Talabani is being treated at a hospital in the Jordanian capital, Amman, after being flown there from northern Iraq earlier in the day.
Mr Talabani is a veteran Kurdish politician
Mr Talabani, 73, had become ill as a result of "continuing hard work over the past few days", his office said.
There was "no cause for concern", it added in a statement.
Deputy Prime Minister Barham Salih said Mr Talabani had suffered a drop in blood pressure, while another ally said he had been having kidney problems.
Mr Talabani, a Kurd, was last seen in public on Saturday in the northern city of Sulaimaniya, where, according to one report, he was hospitalised for several hours.
On arrival in Amman, he was driven directly to the specialist King Hussein Medical Centre, reports said.
Mr Talabani - widely referred to by Kurds as Mam (uncle) Jalal - is one of the longest-serving figures in Iraqi Kurdish politics.
He was sworn in as president in April 2005, after weeks of deadlock in parliament over the appointment to the largely ceremonial post.
Mr Talabani is also the leader of the Patriotic Union of Kurdistan (PUK), one of the two main parties controlling Iraq's Kurdish region.