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In world affairs, posturing among adversaries occasionally calls to mind quaint phrases of childhood. With the latest imbroglio between Israel and the Palestinian Authority, the expressions “He started it” and “Two wrongs don’t make a right” surely fit the bill.

The P.A. “started it” when Palestinian Authority President Mahmoud Abbas requested and was granted an upgrade from the United Nations last week, giving the Palestinians nonmember observer status, or de facto statehood.

While the lopsided U.N. vote suggests the nine nations voting “no” were on the wrong side, the P.A., in putting forward its bid, did an end run around its standing agreements with Israel.

This move may have been born out of frustration with the slow pace toward statehood. But it also was an attempt to isolate Israel, and it opens the door to bringing war crimes charges before international courts. That’s no way for a peace partner to behave.

The 138 nations that voted “yes” on the U.N. vote should be ashamed. They brought peace no closer. On the other hand, Israel’s response was not helpful.

Soon after the vote, Israeli Prime Minister Benjamin Netanyahu announced plans to build 3,000 new homes in eastern Jerusalem and the West Bank, including on E-1, a plot of land adjacent to the Jerusalem suburb of Ma’aleh Adumim.

Palestinians consider Israeli construction there to be a red line, threatening contiguity of an eventual Palestinian state. But a glance at the map shows this to be a dubious claim.

E-1 is a tiny strip running westward from Ma’aleh Adumim to east Jerusalem, in no way bisecting the West Bank. However, it is arguable that Israeli settlements there would cut into the proposed Palestinian capital of east Jerusalem. While most Israelis insist Jerusalem is the undivided capital of Israel, this is a key final status issue that needs to be resolved by the two parties through negotiation.

Netanyahu’s announcement, which triggered harsh worldwide criticism, was an act of bad timing. It took the spotlight off the Palestinian maneuver at the U.N. and shone it onto Israel’s perceived misdoings.

We wish he had been more circumspect. Tit-for-tat politics is not unique to the Middle East, but with the stakes so high for Israel, this may not be the best strategy at this time and in this place. Unilateral steps to create facts on the ground by either side are, in any case, provocative and misguided.