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President-elect Donald Trump has used Twitter — his preferred means of communication — to weigh in on a swath of foreign policy issues over the past few weeks.

His comments give glimpse into how his incoming administration will deal with pressing foreign matters — but also highlight how reactionary comments on social media can immediately spur international concern and attention. And his staff have indicated that taking to Twitter to air his concerns or, often, grievances, won’t end once he enters the Oval Office.

On Wednesday, Trump blasted the U.S.’s abstention from the U.N. Security Council vote on Israeli settlements earlier this month.

The tweets came just hours before Secretary of State John Kerry gave a speech defending their decision and calling the continued building of settlements on Palestinian territory in the West Bank a threat to the two-state solution in the region.

Trump’s support for Israel and Prime Minister Benjamin Netanyahu — who has had a fraught relationship with President Obama — may be the biggest forthcoming shift in immediate foreign policy between the outgoing and incoming administrations. Throughout the campaign, he pledged that his administration would be a steadfast ally of Israel.

To underscore that, Netanyahu replied to one of Trump’s morning tweets, thanking him — and also his children Donald Jr. and Ivanka, who are close advisers — for their support. Ivanka converted to Judaism when she married her husband, Jared Kushner.

An Israeli official told CNN they will give the Trump administration “detailed, sensitive information” proving that the U.S. worked to push through the resolution. The Obama administration has denied those claims.

Last week, after the U.S. decided not to veto the resolution, Trump also tweeted that “things will be different” come his inauguration and then Monday again blasted the U.N. as ineffective.

The Israeli settlement issue has been at the forefront in recent days, but last week Trump also weighed in on nuclear issues. In a tweet, Trump called for the U.S. to strengthen its nuclear arsenal. MSNBC’s “Morning Joe” reported that the president-elect told them he wanted an “arms race. We will outmatch them at every pass.”

As the Washington Post’s Dan Zak told NPR’s Robert Siegel on All Things Considered last Friday, Trump was inconsistent on his statements about nuclear weapons during the campaign.

“Trump said, you know, he’d be the last to use nuclear weapons. Nuclear weapons are a horror. He seemed to understand what they’re capable of doing,” Zak said. “At the same time, he said it was only a matter of time until countries like South Korea and Japan get nuclear weapons. He seemed to tacitly or not so tacitly endorse proliferation, again going against decades of international policy.”

Trump also slammed China for its seizure of an unmanned U.S. Navy underwater drone, calling it “unpresidented” in a tweet before correcting the typo in a new tweet.

After talks with the Pentagon, China agreed to return the drone, but then Trump later said the country should keep it.

It’s not the first time Trump has stoked tensions with China. In a stark break of protocol, Trump spoke on the phone with Taiwan President Tsai Ing-wen earlier this month. Beijing considers Taiwan to be a renegade province and doesn’t recognize it, and most other countries don’t either. The U.S. has operated under a “one China” policy for more than four decades.

Throughout the campaign, Trump blasted China for taking away U.S. jobs and claimed they were intentionally devaluing their currency to boost exports. He’s blasted U.S. companies that manufacture goods in China, but as a New York Times story noted this morning, many of his daughter Ivanka’s clothing and shoe lines are made in China; much of Trump’s own apparel line is also made overseas, including in China.