UPDATE 4-Halliburton says tough to grow revenue 20 pct in '09

* Will struggle to hit revenue growth target of 20 pct

* Profit margin expansion in int'l markets seen limited

* CEO sees no need to change capital spending plans now

* Shares end down 8 percent (Adds CEO quotes on capital spending, exploration, closing stock price)

By Anna Driver

HOUSTON, Nov 19 (Reuters) - Halliburton Co (HAL.N) will struggle in 2009 to meet its long-term goal of increasing revenue by 20 percent a year, due to commodity price volatility and the global financial crisis, the company's chief financial officer said on Wednesday.

Turmoil in world financial markets and a sharp selloff in crude oil and natural gas have prompted energy companies, both large and small, to postpone expensive projects or slow spending on drilling in order to conserve cash.

Shares of Halliburton and others like its larger rival Schlumberger Ltd (SLB.N) have been hammered by worries about steep cuts to exploration spending, the lifeblood of oilfield services firms.

The problem is especially acute in North America, where smaller oil and gas companies have slashed budgets and idled many drilling rigs. On Tuesday, Barclay's capital forecast exploration spending in the U.S. and Canada would fall 25 percent next year before rebounding in 2010.

So it will be "very challenging" for Halliburton to meet its revenue growth target and other financial targets in 2009, CFO Mark McCollum told investors at an analyst meeting, in remarks broadcast over the Internet.

In recent years, Halliburton has grown its revenue 20 percent or better on an annual basis.

Shares of Halliburton ended down about 8 percent, or $1.48, to $16.18 on the New York Stock Exchange. The Philadelphia Stock Exchange index of oilfield service companies .OSX was off 6.6 percent.

Halliburton also will stop repurchasing its shares until it has a better sense that access to capital markets is improving, McCollum said.

"Right now, it's prudent to operate as if cash is king," he said.

Halliburton's priority is reinvesting in the business and keeping its merger and acquisition pipeline full, he said.

For now, the oilfield service company feels situated well enough to weather any downturn and plans to stick to its 5-year capital plan. Halliburton has hired about 14,000 employees so far in 2008, in line with prior years.