UNITED NATIONS (Reuters) - United Nations Secretary-General Ban Ki-moon appealed on Friday for North Korea and South Korea not to take any action that could further escalate tensions after Seoul refused to halt propaganda broadcasts and Pyongyang put its troops on a war footing.

The countries appeared headed toward another clash after South Korea rejected an ultimatum by the North that it halt anti-Pyongyang broadcasts by Saturday afternoon or face military action.

Ban, a former South Korean foreign minister, was deeply concerned by the latest developments, said U.N. spokeswoman Eri Kaneko.

"He urges the parties to refrain from taking any further measures that might increase tensions," Kaneko said. "He also calls on parties to engage in dialogue to reduce tensions and to promote peace and stability on the Korean Peninsula."

Since the 1950-53 Korean War ended in a truce and not a peace treaty, Pyongyang and Seoul have often exchanged threats and dozens of soldiers have been killed, though the two sides have always pulled back from all-out war.

(Reporting by Michelle Nichols, editing by G Crosse)