Canadian Imperial Bank of Commerce (CM.TO) said on Thursday it would be "disciplined" in assessing whether to raise its $3.8 billion offer for Chicago-based PrivateBancorp and could step up stock buybacks if the deal collapses.

The bank announced what would be its biggest acquisition in June last year, but the plan has been in doubt since PrivateBancorp postponed a shareholder vote to approve it in December after some investors said they would reject the offer.

CIBC is weighing its options ahead of a deadline in June and could decide to raise its offer or walk away.

Speaking after the bank posted better-than-expected quarterly results, CIBC Chief Executive Victor Dodig said he believed the deal was still in the best interest of CIBC and PrivateBancorp (PVTB.O) shareholders but emphasized the bank would take a "disciplined" approach to the proposed takeover.

"They're a good bank," he said. "We've been working with them for a long, long time, we've got good integration plans under way, but we will be disciplined and we will be patient when it comes to price."

He added: "We may have to be more active in terms of buying back stock over time if we're not able to consummate that deal in this period of time; we want to make sure those avenues are open to us."

CIBC reported a 13 per cent rise in earnings in the first quarter to Jan. 31, helped by growth in its retail and capital markets businesses.

Adjusted net income rose to $1.17 billion, or $2.89 per share, after excluding one-off items such as restructuring charges and gains on the sale and lease back of retail properties.

That surpassed the average analyst forecast of $2.59 per share, according to Thomson Reuters I/B/E/S.

CIBC's core tier 1 capital ratio, a key measure of its financial strength, improved to 11.9 per cent in the last quarter, the best of any Canadian bank.

The bank said its retail and business banking division earned adjusted net income of $709 million, up from $686 million a year earlier, while its capital markets business reported adjusted net income of $371 million, up from $244 million.