President Yoon Suk Yeol speaks at the World Economic Forum on Jan.19 in Switzerland. (Yonhap)

South Korea and the United States are in talks over a possible state visit to Washington by President Yoon Suk Yeol in the first half of the year, a diplomatic source said Friday.

If it materializes, it would be the first state visit to the United States by a South Korean president in 12 years. President Lee Myung-bak was the last president to pay such a visit to Washington in 2011.

The source said the allies are keeping other options open, such as an official visit or a working visit. April is seen as the most likely time for the trip.

A state visit is the highest form of a visit by a head of state, and is typically accompanied by an official welcome ceremony, an inspection of an honor guard, a state dinner and an address to Congress.

Yoon's visit would coincide with the 70th anniversary of the two countries' alliance at a time when his administration is seeking a closer alignment with Washington on both security and economic issues.

The presidential office said it has no details to reveal as of now, given that it is customary for the two countries to simultaneously announce a state visit and the need to consider the congressional calendar.

"The two countries are in talks over a US visit, and nothing has been decided yet," a senior presidential official said.