CARSON (CBSLA.com) — A labor strike at a Carson petroleum plant and other sites nationwide is among several key factors likely to push gas prices back up over the $3-per-gallon mark, analysts said Monday.

About 800 workers at the Tesoro refinery in Carson have walked out on strike demanding higher pay increases, lower health care payments, more work and higher safety standards for union members, according to union officials.

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Tesoro received strike notifications at its refineries in Carson, Martinez, Calif., and Washington state, after the USW collective bargaining agreements expired on Jan. 31.

While Tesoro officials say they’re confident that the company can continue to safely operate the refineries and meet customer commitments, the strike could combine with other market forces to put upward pressure on gas prices.

Gregg Laskoski, Senior Petroleum Analyst at GasBuddy.com, told KNX 1070 NEWSRADIO it’s only “coincidental” that the Tesoro strike is occurring as prices head higher.

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“This is what would be happening regardless of whether an oil strike or refinery workers’ strike was occurring, simply because we have the transition from winter blend gasoline to summer blend,” said Laskoski. “As a result, we’re seeing wholesale prices climb significantly.”

The trend is expected to mark the end of four consecutive months of declining prices at the pump.

Prices are projected to trend upward and peak sometime between May and July, pushing the national average “slightly above” $3 per gallon, according to Laskoski.

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While the national average for 2015 is expected to end up around $2.60 per gallon, drivers throughout California will face prices well above $3 until at least after the summer, Laskoski said.