Senior diplomats of South Korea and the United States had a phone conversation Wednesday to discuss North Korea's recent missile tests and reaffirmed the bilateral alliance's efforts to tackle regional challenges, the foreign ministry said.

Seoul's First Vice Foreign Minister Choi Jong-kun and his US counterpart Wendy Sherman talked over the phone after Pyongyang said it test-fired two tactical guided missiles Monday, the fourth show of force this month alone.

"The vice ministers shared their assessments of North Korea's string of missile launches and reaffirmed that they are open to all options to stably manage the situation on the Korean Peninsula and resume talks with the North at an early date," the ministry said in a release.

In a separate statement, the State Department said Sherman condemned North Korea's "recent ballistic missile launches, which were in violation of multiple UN Security Council resolutions, and discussed continued joint efforts to achieve the complete denuclearization of the Korean Peninsula."

High-level Seoul and Washington diplomats have held back-to-back phone talks following Pyongyang's new weapons tests, including of two self-proclaimed hypersonic missiles, amid stalled denuclearization talks.

Last week, the Joe Biden administration blacklisted six North Koreans in its first sanctions against the reclusive regime's ballistic missile tests, and is leading a campaign within the UN Security Council to extend its own sanctions.

During their conversation, Choi gave a briefing of his recent meetings with top negotiators of the ongoing Iran nuclear talks in Vienna, stressing the importance of the bilateral collaboration to restore the 2015 nuclear deal and resolve issues related to Tehran's frozen assets, the ministry said.

In response, Sherman agreed on the need to promptly settle the Iranian issue and appreciated Seoul's support for Washington's diplomatic efforts, it noted.

South Korea is not directly related to the Iran nuclear deal, but it has been exchanging views with the negotiators as Tehran's $7 billion funds are locked in two Korean banks under US sanctions imposed by the administration of former US President Donald Trump. (Yonhap)