A "vaccine swap" agreement that South Korea is looking at with the United States could be a loan deal in which the country receives surplus COVID-19 vaccines from the US and gives the same amount back later, sources said Tuesday.

Foreign Minister Chung Eui-yong said during a parliamentary session earlier in the day that the country is discussing a "vaccine swap" arrangement with the US "fairly seriously" and the issue was a key focus in his talks with US Special Presidential Envoy for Climate John Kerry, who visited Seoul last week.

Chung did not elaborate on what a swap deal means.

Foreign ministry spokesperson Choi Young-sam also declined to provide details, only saying that the country is making multifaceted efforts in terms of vaccination cooperation with the US.

But sources said that one of the possible options is to strike a loan deal with the United States under which South Korea receives vaccines that the US is not using, and gives the same amount back after the country is provided with its own vaccines.

The US has similar deals with Canada and Mexico.

White House spokesperson Jen Psaki said last month that the US has "7 million releasable doses" of the AstraZeneca vaccine and was working on arrangements to loan 1.5 million doses to Canada and 2.5 million doses to Mexico.

The AstraZeneca vaccine has not yet been approved for use in the US. (Yonhap)