Sept 13 (Reuters) - A strike beginning Friday by more

than 30,000 of Boeing's ( BA ) U.S. West Coast factory workers will

make it harder for the planemaker to meet a 737 MAX production

target and stabilize its supply chain, CFO Brian West said on

Friday.

West also told the Morgan Stanley Laguna Conference he

expects third-quarter margins from the company's defense and

space unit to be negative, similar to those in the second

quarter.

Workers from Seattle and Portland, Oregon, who produce the

MAX and other jets walked off the job after overwhelmingly

rejecting a contract deal due to demands for higher pay. The

workers' first strike since 2008 comes as Boeing ( BA ) is under heavy

scrutiny from U.S. regulators and customers after a door panel

blew off a 737 MAX jet mid-air in January.

West said Boeing ( BA ) had made progress towards ramping

production of its strongest selling jet back to 38 a month by

year's end,

despite earlier skepticism

from rating agencies over the target.

"We've been making good progress on stabilizing

production and preparing for that 38 per month by the end of the

year. Now, obviously that's going to take longer," West said.

West, however, would not comment on specifics related to

the target, which depends on the duration of the strike.

The strike is creating more uncertainty and concern for

suppliers of parts and components for programs like the 737 MAX.

Many were already having difficulty planning production due to

Boeing's ( BA ) repeated changes to internal forecasts for suppliers.

West said a company priority was stabilizing its supply

chain, but that "objective just got harder."

West suggested Boeing ( BA ) would stop taking parts from some

suppliers on programs impacted by the strike where the

planemaker has ample inventory. The company's 787 widebody jet

is not impacted, as it is built in South Carolina by a

non-unionized workforce.

Asked about supply chain, West said for non-787

programs, if the supplier is not behind and the company has

enough stock, "you know, don't deliver anymore."

He said this messaging is "happening overnight and as we

speak."