(Reuters) - Copper fell to a one-week low on Friday after weaker-than-expected U.S. jobs data increased uncertainty about economic growth, but tight supplies of the metal outside China kept losses in check.

Benchmark copper on the London Metal Exchange slipped to its lowest level since April 26 in intraday trade at $8,192 a metric ton (1.1023 tons), before recovering to $8,222 a ton at 9.25 a.m. EDT, from a close of $8,229 a ton on Thursday.

U.S. employers slowed the pace of hiring for a second straight month in April, and a fall in the unemployment rate to 8.1 percent was due to the exit of a large number of Americans from the labor force. Nonfarm payrolls rose by 115,000 in April, the Labor Department said, against a forecast of 170,000.

The macro numbers are becoming worse, especially in the U.S., so it's going to be difficult for a lot of these metals to hold up, Edward Meir, an analyst at INTL FCStone, said.

The French elections will also be important, because then the euro might move on that and give the market a bit more direction, he said, referring to polls over the weekend.

Market players said they expect large Chinese copper smelters and trading firms to export refined copper cathodes to LME-registered warehouses over the next two months to help ease tight global supplies and trim near-record stockpiles at home.

As a result, thousands of tons of refined copper could go into LME warehouses, boosting inventories and slashing steep premiums of spot prices over those for later deliveries.

Copper might get down to $7,800 a ton during the course of the month. The $8,000 level keeps holding up, but this level could break once the stock picture changes. If you start seeing accumulations for a few days in a row, then that's when the pressure will be on, Meir said.

Inventories of copper in warehouses monitored by the Shanghai Futures Exchange fell 4.0 percent from last Friday to their lowest since February, data showed. Copper stocks in LME-monitored warehouses also fell, reaching their lowest since October 2008.

SUPPLY RESPONSE

Investors were balancing this with supply tightness worries as Chile once again struggled with lower-than-expected copper production and labor action, which heightened risks to supply.

A protest took place this week at Chile's giant Escondida copper mine, the world's largest, as a group of contract workers blocked some roads to the deposit in a dispute over bonuses.

Although majority owner BHP Billiton (BHP.AX) (BLT.L) said on Thursday output had not been affected, worries lingered.

People are skeptical of miners' comments as producers always tend to underestimate production disruption. They said the same last year and then they actually were impacted, Credit Suisse analyst Ivan Szpakowski said.

Also highlighting supply scarcity, first-quarter copper production at Chilean miner Antofagasta (ANTO.L) fell 13 percent on the previous three months amid rising development costs, the London-listed firm said.

With real demand in China now starting to increase and global industrial output trending higher, the ability of supply to respond is likely to drive relative performance in H2, Macquarie said in a research note.

Aluminum was at $2,082.50 a ton from $2,089.50 and nickel was at $17,451 from $17,275.

Both were supported by news that Indonesia will impose a new 20 percent export tax on 14 mineral ore exports including copper, gold and nickel from Sunday and will prohibit the shipment of raw minerals unless miners submit plans to build smelters.

This is likely to hit exports of nickel and bauxite to China and push ore prices higher, an industry source said.

Zinc, used in galvanizing, was at $1,990 from Thursday's close of $1,984, battery material lead traded at $2,085.75 from $2,092 and tin was at $21,750 from $21,805.

(Editing by Mike Nesbit and Jane Baird)