Openers Sami Aslam (31 not out) and Shan Masood (30 not out) negotiated 23 overs to take Pakistan to 64-0, still trailing Sri Lanka's first-innings total of 419 by 355 runs.
They need another 156 to avoid the follow-on, a task which should be simple on a flat Sheikh Zayed Stadium pitch.
Both Masood and Aslam, opening for the first time together, looked assured as Sri Lanka attacked through all their three spinners and two seamers in short spells.
But it was a memorable day for Sri Lankan skipper Chandimal, whose marathon knock of over nine hours in hot conditions propelled his team to a strong total.
He came in to bat with his team in trouble at 61-3 on Thursday, but led the fightback in a fourth-wicket stand of 100 with Dimuth Karunaratne (93).
Pakistan Playing XI: Shan Masood, Sami Aslam, Azhar Ali, Asad Shafiq, Babar Azam, Haris Sohail, Sarfraz Ahmed (c & wk), Mohammad Amir, Yasir Shah, Mohammad Abbas, Hasan Ali
Sri Lanka Playing XI: Dimuth Karunaratne, Kaushal Silva, Kusal Mendis, Dinesh Chandimal (c), Lahiru Thirimanne, Niroshan Dickwella (wk), Dilruwan Perera, Rangana Herath, Suranga Lakmal, Lakshan Sandakan, Nuwan Pradeep
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First Published: September 30, 2017, 11:19 AM IST