Sinn Fein president Gerry Adams is expected to announce later that he intends running for the Irish parliament in the next election.
If successful, it would mean he would hold a seat at Westminster, Stormont and in Dublin at the same time.
His decision to run for a seat in the Dail would mark a significant change in strategy by the Sinn Fein leader, says BBC correspondent Mark Simpson.
He has always concentrated on electoral politics north of the border.
The Irish prime minister, Brian Cowen, must call a general election before July 2012 and it is thought the election may happen next year.
As the peace process has settled down in recent years, Sinn Fein president Gerry Adams has often looked bored.
There is no longer a new political crisis every week in Belfast. As a result, Mr Adams has a reduced workload and a much lower profile.
That may not be the main reason he has decided to run for the Irish parliament, but it may well be a factor.
While his right-hand man Martin McGuinness has become the face of Sinn Fein at Stormont, as Deputy First Minister, Mr Adams has had a peripheral role.
He spends a lot of time south of the border, but as an unelected politician he is effectively shouting from the sidelines.
At 62, he has decided to try to re-invent himself. If he wins a seat in the Irish parliament, he is likely to step down from Stormont and concentrate on southern politics.
If he loses it could spell the end of his long political career.
An obvious seat for 62-year-old Mr Adams to attempt to win would be in County Louth, just across the border from Northern Ireland.
Louth is currently represented by Sinn Fein’s Arthur Morgan, who has said he plans to step down at the next election.
Mr Adams is due to deliver the keynote address at the Edentubber Commemoration in County Louth later on Sunday.
In a brief statement issued on Saturday night, the party promised a “significant” speech from its leader at the commemoration.
Sinn Fein has five MPs, including Mr Adams, and four TDs in the Irish parliament.
There is no modern precedent for a politician to seek election to both Westminster, where Mr Adams represents West Belfast, and the Dail.
Our correspondent said if elected to the Dail, Mr Adams would probably step down from Stormont to concentrate on politics south of the Irish border.
Mr Morgan was elected to Louth County Council in 1999, before taking the seat in the Dail at the 2002 general election, and retaining it five years later.
Last week he announced he would be stepping down at the next election to concentrate on his business. He said the party leadership had accepted his decision.
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