Usman Khawaja and Steven Smith consolidate for Australia

Tea Australia 172 for 2 (Khawaja 86*, Smith 40*) vs Pakistan

Usman Khawaja neared a century in the city his family hails from, as Australia blunted Pakistan's attack during a sedate second session on day one of the second Test in Karachi.

Australia reached tea on 172 for 2 with Pakistan-born Khawaja 86 not out and Steven Smith unbeaten on 40 as the pair batted through the session after Pat Cummins won a crucial toss in Pakistan's fortress of Karachi.

Mixing exquisite strokes with watchful defence, Khawaja closed in on a third century in his last six innings after being recalled during the SCG Ashes Test in January. The remade opener agonisingly missed out on adding another in Rawalpindi having top-scored with 97 in Australia's sole innings.

A determined Smith, who has scored only one ton in his last 27 Test innings, batted patiently and he was content with stonewalling Pakistan's attack as just 72 runs were scored in a dour middle session.

There has been much intrigue over conditions in Karachi after the historic series, the first between the teams in Pakistan since 1998, started with a dreary draw due to a lifeless Rawalpindi pitch rated by the ICC as below average. But it has been more of the same with conditions skewed towards the batters although reverse swing was evident before tea to change the complexion of the contest.

Untroubled in the first session, Khawaja confidently fended off a bumper barrage after lunch from Shaheen Shah Afridi who hasn't quite hit top gear he consistently found in the series-opener.

After Khawaja scored briskly through the first session, Pakistan were able to stymie the run rate late in the second session through accurate bowling from Shaheen and Faheem Ashraf, who both started to conjure reverse swing.

There hasn't been much of a spin threat although left-armer Nauman Ali, fresh off his career best six-wicket haul in Rawalpindi, found bounce and occasional turn in a promise of what might be ahead on a pitch expected to break.

Hasan Ali, who returned from an abductor strain, struggled to consistently probe having replaced fiery quick Nassem Shah, who impressed in Rawalpindi with menacing short-pitched bowling.

Australia regained control after losing the key wickets of David Warner and Marnus Labuschagne before lunch in a lively opening session. Warner fell on 36 to a gem of a delivery from returning pace allrounder Ashraf, who squared up Warner to entice an edge to wicketkeeper Mohammad Rizwan.

Shortly after Labuschagne, who made 90 in Rawalpindi and is the No.1 ranked batter in the world, was run out for a duck by a direct side-arm throw from Sajid Khan after attempting a risky single. The quick wickets undid a dominant first hour for Australia after Khawaja and Warned weathered challenging early bowling from Pakistan's pacemen.

A cautious Warner struggled against the new ball and survived two tight lbw shouts from Hasan bowling around the wicket before finding his groove against Sajid, hitting the offspinner for a couple of sixes.

For the second straight innings, Warner rued missing out on a strong start but Australia got back on track through Khawaja and Smith as they eye a formidable first innings total in a bid to rouse their tweaked attack.

In their only change, Australia handed legspinner Mitchell Swepson his long-awaited Test debut having been around the squad since 2017. The 28-year-old replaced quick Josh Hazlewood to become the first specialist legspinner capped by the Australian men's Test team since Bryce McGain in 2009.

Australia will be hoping it's a while before Swepson has a bowl as they aim to make Pakistan toil under hot conditions in Karachi, where the temperature has hovered over 30 degrees in a contrast to Rawalpindi's mild conditions last week.

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Tristan Lavalette is a journalist based in Perth