UPDATE 3-US FCC chief near deal for XM-Sirius approval

(Recasts first paragraph, adds analyst comment, closing stock prices)

By Peter Kaplan

WASHINGTON, July 23 (Reuters) - The merger of the two U.S. satellite radio companies was poised for approval as a pivotal member of the Federal Communications Commission neared agreement to cast a tie-breaking vote in favor of the deal, a source familiar with the merger review said on Wednesday.

FCC Chairman Kevin Martin was close to getting the support of fellow Republican commissioner Deborah Taylor Tate to reach the three votes needed to approve Sirius Satellite Radio Inc's (SIRI.O: Quote, Profile, Research, Stock Buzz) purchase of XM Satellite Radio Holdings Inc XMSR.O, the source said.

Tate's support would break a 2-2 deadlock on the five-member commission and split the vote down party lines.

A vote on the deal, worth $3.9 billion at Wednesday's closing stock prices, could come as early as this week, another source familiar with the merger review said.

As part of the approval, the FCC will require the companies to pay a $20 million fine for alleged past violations of FCC rules, this source said.

Democratic FCC Commissioner Jonathan Adelstein cast his vote against the deal on Wednesday morning after he and Martin could not come to terms on additional conditions Adelstein wanted to impose.

FCC approval is the last obstacle in a regulatory marathon for the merger that was first announced in February 2007. Antitrust authorities at the U.S. Justice Department gave their approval in March.