WASHINGTON—A bilateral market access agreement reached in principle between the United States and Russia that would bring Russia into the World Trade Organization is being hailed by U.S. insurers as opening the door to a potentially lucrative new marketplace.

But getting that door opened even a crack wasn't easy, said David Snyder, vp and assistant general counsel for the American Insurance Assn. in Washington. Negotiations took at least five years, he noted.

"Insurers generally view Russia as a potentially significant market, but to get to this point, we have had a very difficult set of negotiations," Mr. Snyder said. "The end result...is good in that U.S. companies will be able to establish the way they would like to operate in Russia and write all lines of insurance after a several year phase-in period."

Three major obstacles had to be overcome, he said. The first was to allow foreign insurers to set up branches in Russia rather than requiring them to set up a Russian company, he said.

The second was Russian resistance to allowing U.S. insurance companies to write what he called "certain very large lines of nonlife insurance," such as third-party automobile liability.

The last was Russian insistence on placing an overall limit on foreign participation in the insurance market. "While that cap still exists, there are many exceptions" that were negotiated and "we don't think it will be commercially significant," said Mr. Snyder.

According to a Nov. 10 fact sheet released by the Office of the U.S. Trade Representative, "Russia retains the discretion to impose limits on new foreign direct investment in the banking and insurance sectors, if the ratio of foreign investment (excluding many investments) to total investment in the sector exceeds 50%."

The two nations planned to sign the bilateral agreement last week at the Asia-Pacific Economic Cooperation meeting in Hanoi, Vietnam.

Mr. Snyder said that, barring any unexpected issues, Russia should join the WTO next year.

Bringing Russia into the WTO is "good for everyone," as it opens the markets a little more broadly for business including insurance, said Coletta Kemper, vp-industry affairs for the Council of Insurance Agents & Brokers in Washington.

"The brokerage market has been, in practice, fairly open in Russia," said Ms. Kemper. "Certainly we're looking for--and we hope that their inclusion in the WTO will improve--commitments we've gotten with transparency, which was a big issue for the insurance industry."

"Transparency is obviously important so people know what the rules and regulations are," Ms. Kemper said. "It's important to know what you need to do as an organization to function in a country."

She also called the agreement to allow branching and--after a transition period--100% foreign ownership of nonlife companies "a major step forward."

Insurance is only one of a broad range of economic sectors affected by the bilateral agreement. Others include business services, banking and securities, manufactured goods and agricultural products.

Russia also agreed to fight against piracy and counterfeiting and otherwise to improve protection of intellectual property rights.