LONDON/WASHINGTON, Dec 3 (Reuters) - U.S. Secretary of State Antony Blinken told the Reuters Next conference on Friday that Chinese leaders should think carefully about their actions toward Taiwan, warning of "terrible consequences" if China precipitates a crisis across the Taiwan Strait. In an interview, Blinken addressed multiple foreign policy challenges facing the administration of President Joe Biden, including faltering efforts to repair the 2015 Iran nuclear deal, Russia"s military buildup near Ukraine, and the spiraling conflict in Ethiopia. Most acute may be China"s increasingly aggressive posture toward Taiwan, which Beijing claims as its territory. Taiwan"s defense minister has said tensions with China are at their worst in more than 40 years adding that China will be capable of mounting a "full-scale" invasion by 2025. Asked if China was going to invade Taiwan, Blinken said “that would be a potentially disastrous decision," repeating Washington"s position that it is "resolutely committed" to making sure Taiwan has the means to defend itself. China had been trying to change the status quo across the Taiwan Strait in recent years by engaging in provocative military maneuvers and trying to isolate Taiwan from the rest of world, Blinken said. read more “I hope that China’s leaders think very carefully about this and about not precipitating a crisis that would have I think terrible consequences for lots of people and one that’s in no one’s interest, starting with China," Blinken said. U.S. Secretary of State Antony Blinken addresses a press conference during a ministerial council meeting of the Organisation for Security and Cooperation in Europe (OSCE) in Stockholm, Sweden, December 2, 2021. Jonathan Nackstrand/Pool via REUTERS U.S. Secretary of State Antony Blinken addresses a press conference during a ministerial council meeting of the Organisation for Security and Cooperation in Europe (OSCE) in Stockholm, Sweden, December 2, 2021. Jonathan Nackstrand/Pool via REUTERS China remains Biden"s number one foreign policy priority, but his administration has also been buffeted by crises elsewhere. Blinken said the United States had sanctions it could use for parties perpetuating Ethiopia"s conflict. read more On Iran, Blinken said Washington ended indirect talks in Vienna this week because Tehran did not seem serious about a return to compliance with the nuclear deal. read more "If the path to a return to compliance with the agreement turns out to be a dead-end, we will pursue other options," he said. Blinken returned on Thursday from Europe, where he met Russian Foreign Minister Sergey Lavrov and delivered a warning over Russia"s military buildup near Ukraine. Biden is expected to speak to President Vladimir Putin in the near future, and will tell the Russian leader that Washington is determined to stand up against any "reckless or aggressive" actions, Blinken said. The United States wants a more predictable relationship with Russia, he said. read more “There are areas where we have overlapping interests and we should be able to work together if we can have some stability and predictability in the relationship. Russia’s actions and the threat of further aggression against Ukraine moves in exactly the opposite direction," Blinken said.