The Dynamos finished 143-1 following a century stand from openers Scott Borthwick (70*) and Mark Stoneman (56), which leaves them just 60 runs behind the Sri Lankans.
The tourists won the toss and elected to bat first in overcast conditions at the Emirates Durham ICG.
Openers Malindu Warnapuna and Lahiru Thirimanne found the opening overs hard going as Durham bowlers Ruel Brathwaite and Chris Rushworth bowled very tight lines.
This accuracy paid off for Brathwaite as he snared the wicket of Warnapura in the fifth over trapping him in front of the wickets, LBW for 10.
Thirimanne followed his opening partner back to the pavilion in the next over as he was caught in the slips by Gareth Breese after knicking a good ball from Rushworth for one.
Brathwaite continued to impress in his opening spell and got the third wicket of the Sri Lankan innings when he had Dimuth Karunaratne caught behind by wicket-keeper Michael Richardson for seven.
This brought the visitors captain Kashaul Silva to the crease but he didn’t last long as he fell to Mark Wood’s first delivery as he was caught behind by Richardson for one to leave the tourists 36-4.
Bhanuka Rajapaksa and Sacithra Serasinghe halted the Sri Lankan collapse and battled against some great bowling from the Dynamos attack to move the visitors past 50.
The pair had reached a partnership of 39 before Rajapaksa fell to Wood as he was caught behind by Richardson to leave the Sri Lankans in deep trouble at 75-5.
Serasinghe was joined at the crease by Kosala Kulasekera who help steady the innings while Serasinghe went on the offensive crashing eight boundaries in his innings of 44 as the tourists moved past the 100 mark. Their stand of 30 was ended when Serasinghe went for one big shot too many and was caught at mid-on but Wood off the bowling of Rushworth.
Brathwaite returned to the Durham attack to remove Sacithra Senanayake for 2 as the Dynamos looked to finish the visitors innings quickly.
However Shaminda Eranga was not going to allow the tourists innings end without a fight as he crashed seven boundaries including one six in his unbeaten knock of 50 off just 61 balls.
He was aided by Sajeewa Weerakoon and Nilanka Premaratne who hit 18 and 11 respectively before they were removed by Borthwick as the tourists finished their innings 203 all out.
Durham opening batsmen Stoneman and Borthwick started their innings cautiously as the new ball moved around off wicket in the opening overs.
However both soon got the grips with the Sri Lankan bowlers as the shine began to wear off the new ball and the pair found the boundary at regular intervals.
Both batsmen looked comfortable against the spin and pace options in the tourists line-up and it was Borthwick who reached his 50 first in the 24th over with a huge six off spinner Senanayake, as the opening pair posted a 100
partnership for the first wicket.
Stoneman’s 50 followed in the next over however he soon departed for 56 as he edged a ball from Premaratne behind to the visitor’s wicket-keeper Silva ending the opening stand of 117.
Borthwick was joined in the middle by skipper Gordon Muchall and the pair ended the day strongly with the all-rounder in particularly in control as he finished 70* as the Dynamos closed on 143-1.