Tseng and his northern counterpart, General Singh Manh Li, attended a peace conference to reunite the two nations. After an assassin attempted to murder the independent arbitrator they had brought in, Lex Luthor, both Li and Tseng accused each other of hiring her.
Luthor was eventually able to unite the two leaders, who gave all credit to Luthor, though Red Arrow and Aqualad prevented Cheshire from succeeding.
Some time after his term as prime minister was complete, Tseng was appointed Secretary General of the United Nations. He was abducted by the Kroloteans, imprisoned in their New Orleans base, and replaced by a robotic duplicate controlled by a Kroloteanaround December 2015.
Tseng was present at the United Nations press conference where Captain Atom met publicly with the Reach ambassador. Captain Atom indicated some issues needed to be discussed privately.
New York City April 1, post-21:24EDT
The private discussions saw Captain Atom and the Reach ambassador each hurl accusations at one another. When the ambassador brought up young operatives who worked on behalf of the Justice League, Tseng told Captain Atom he knew about the young heroes. Captain Atom replied that the Reach had been kidnapping humans, but the ambassador claimed he was confusing the Reach with the Kroloteans. Tseng asked for proof of Captain Atom's accusations, but Captain Atom was interrupted by a communications message about an attack at the Hall of Justice.
Tseng later arrived with the Reach ambassador at the now-destroyed Hall, which was surrounded by a force field. The ambassador used a device to remove the field and told Captain Atom the League was fortunate to still have the Watchtower. Tseng, who didn't know anything about the Watchtower, was surprised at this fact.
After Captain Atom provided holographic proof that the Reach had intended to enslave the Earth all along, Tseng conducted an emergency session of the United Nations. After a unanimous vote, he officially rescinded the Reach's invitation to stay on Earth, and demanded that they leave immediately.
Before leaving the Earth, the Reach planted numerous doomsday weapons to destroy evidence of their tampering. The activation of the weapons caused severe weather disruptions throughout the planet. When Lex Luthor requested access to Tseng's private frequency with the Justice League in order to offer his assistance, the embattled secretary-general acquiesced.
After G. Gordon Godfrey continually (and hypocritically) criticized his "disastrous collaboration" with the Reach, Tseng tendered his resignation, leaving the post of UN Secretary General vacant. Although no replacement was announced, Godfrey enthusiastically promoted Luthor as the most logical candidate.