Hours after saying he had decided to form an "impenetrable Cyber Security unit" with Russian President Vladimir Putin, President Trump on Sunday night abruptly pulled back on his endorsement.

Trump's original tweet was widely mocked given U.S. intelligence conclusions that Russia hacked into the servers of several American political organizations in the last election.

GOP Sens. Lindsey Graham Lindsey Olin GrahamSenate Republicans face tough decision on replacing Ginsburg Democratic senator calls for eliminating filibuster, expanding Supreme Court if GOP fills vacancy What Senate Republicans have said about election-year Supreme Court vacancies MORE (S.C.) and John McCain John Sidney McCainMcSally says current Senate should vote on Trump nominee Say what you will about the presidential candidates, as long as it isn't 'They're too old' The electoral reality that the media ignores MORE (Ariz.) both said Putin could not be trusted to cooperate in any joint cyber effort with the U.S.

Trump's tweet on Sunday night appeared to have been in response to some of this criticism.

“The fact that President Putin and I discussed a Cyber Security unit doesn't mean I think it can happen. It can't-but a ceasefire can,& did!” Trump tweeted on Sunday about three hours after tweeting about a cease-fire in Syria.

The fact that President Putin and I discussed a Cyber Security unit doesn't mean I think it can happen. It can't-but a ceasefire can,& did! — Donald J. Trump (@realDonaldTrump) July 10, 2017

The cease-fire refers to a separate agreement between the U.S. and Russia aimed at ending fighting in southern Syria, which is in the midst of a yearslong civil war.

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That agreement may have been the biggest concrete success from Trump's meeting with Putin on the sidelines of the annual G-20 summit. Russia is a key ally of Syrian President Bashar Assad.

Social media users reacted quickly to Trump’s tweet knocking his own proposal.

Trump is basically admitting his own attempts at diplomacy are useless? pic.twitter.com/jfEqzK45uF — Olivia Nuzzi (@Olivianuzzi) July 10, 2017

Well that is clarifying https://t.co/6f2wXGvKTc — Eric Michael Garcia (@EricMGarcia) July 10, 2017

I have no idea what our president is saying. But maybe it was clearer in the original Russian? https://t.co/Cvw8jiKiyO — Nicholas Kristof (@NickKristof) July 10, 2017

is this performance art? https://t.co/Drydq5Vq7H — Sam Stein (@samstein) July 10, 2017

Test Balloon Disavowed https://t.co/VJbjUqyJ61 — Jared Rizzi (@JaredRizzi) July 10, 2017

Well that didn't last long https://t.co/tTxKL72K1l — Tom Namako (@TomNamako) July 10, 2017