TOKYO (Yonhap News) -- Three Japanese lawmakers vowed Saturday they will go ahead with their trip to a Korean island next week, a day after Seoul formally informed Tokyo that it will bar them from entry.

Korea quickly reaffirmed its stance on Saturday that immigration officials will deny entry to the lawmakers upon their planned arrival at an airport on Monday and send them back to Japan.

The looming diplomatic spat could worsen the relations between the two neighbors, which have often been strained by historical disputes stemming from Japan's 1910-45 colonial rule of the Korean Peninsula.

The latest dispute centers on the lawmakers' planned trip to Ulleung Island, the closest Korean territory to its easternmost islets of Dokdo over which Japan has frequently laid claim.

Korea suspects the high-profile trip to Ulleung Island by the Japanese lawmakers could be an attempt to reassert Tokyo's territorial claims to the cluster of rocky outcroppings.

Japan's sovereignty claims to Dokdo have long been a key source of diplomatic friction in relations with Korea, where many people still harbor deep anti-Japanese resentment for its brutal colonial rule.

Korea has lodged a formal protest with the top Japanese envoy in Seoul against the planned visit and warned that the lawmakers' safety cannot be guaranteed.

Still, Yoshitaka Shindo, a lawmaker of the conservative Liberal Democratic Party, said in a news conference that he and his two fellow legislators will travel to Korea on Monday for a four-day trip.

He warned that Seoul's decision to bar the lawmakers' entry would have a negative impact on relations between Seoul and Tokyo.

Initially, four lawmakers had planned to visit Korea, though a lawmaker later dropped out due to scheduling conflicts.

In early July, Japan imposed one-month ban on the use of Korean Air flights by its diplomats in retaliation for the airline's June

16 test flight of its first Airbus A380 plane over Dokdo.

Korea demanded Japan immediately withdraw the measure, but Tokyo has refused to do so. (Yonhap News)