Republican sources say six-term Rep. Jim Greenwood (R) has informed the House Republican leadership that he will retire at the end of the 108th Congress, a decision that adds another competitive race to both the Democratic target list and the Pennsylvania election map.

While Greenwood said in a statement Monday that he had not yet made a final decision, two knowledgeable sources confirmed that Greenwood told the leadership he definitely plans to retire.

The timing of the 53-year-old’s formal retirement announcement remains unclear, however. One House Republican source said it would likely come later this week.

“From time to time during my 24 years of public service, I have been approached and offered other types of challenges and opportunities,” Greenwood said in his statement Monday. “Such has been the case in the last few days, and I am currently reviewing one of these opportunities. I will make my decision public in the very near future and will have no other statement until then.”

Greenwood, a moderate who has been active on health care issues, is a leading contender to run the Biotechnology Industry Organization, according to biotechnology lobbying sources. Other finalists for the BIO post include retiring Rep. Cal Dooley (D-Calif.) and Karen Ignagni, the current president and CEO of America’s Health Insurance Plans.

Greenwood is the fifth prominent centrist Republican to announce his retirement this Congress, following Reps. Jack Quinn (N.Y.), Doug Ose (Calif.), Doug Bereuter (Neb.) and Amo Houghton (N.Y.).

As is the case in Quinn’s seat, Republicans will now have to pour resources into Greenwood’s district if they want to keep it in the GOP column.

“It clearly turns that into a wide-open race,” said Mike O’Connell, a GOP consultant and the current executive director of the Allegheny Republican Party across the state in Pittsburgh.

The 8th district consists almost entirely of Bucks County, an affluent suburb northeast of Philadelphia. The district, which also includes small portions of Montgomery County and the city of Philadelphia, has remained virtually unchanged during recent redistricting cycles.

The seat, like most Philadelphia suburbs, has trended more and more Democratic in recent years, and it voted overwhelmingly for former Philadelphia Mayor Ed Rendell (D) in the 2002 gubernatorial race.

In the 2000 presidential contest, Vice President Al Gore won the district with 51 percent over George W. Bush’s 46 percent.

Because Pennsylvania’s primary has already passed, it will be up to state and local party leaders to govern the process by which a replacement candidate will be chosen.

Calls to the Pennsylvania Republican State Committee were not returned Monday.

To replace Greenwood on the ballot, delegates from the counties that make up the 8th district will meet in what amounts to a nominating convention to select a new GOP nominee.

The party chairmen in each county have virtually unchecked authority to appoint delegates to the convention. The total number of representatives each sends is proportional to county population.

Since the district consists almost entirely of Bucks County, GOP Chairman Harry Fawkes will hold great sway over the selection process.

At least three names were being floated Monday as possible replacement candidates, a list that includes two state Senators and a Bucks County official.

State Sen. Joe Conti, who holds a legislative seat once filled by Greenwood, is described as a traditional northeastern Republican who would fit well in the socially moderate mold of the current incumbent.

State Sen. Robert “Tommy” Tomlinson (R) hails from the more Democratic part of Bucks County and represents a blue-collar, heavily Catholic constituency. Tomlinson’s anti-abortion views could hurt his chances against a well-funded Democrat in a swing district and a presidential election year.

In 2002, Tomlinson was re-elected in a close race against former Rep. Peter Kostmayer (D), who represented the 8th Congressional district before losing to Greenwood in 1992.

Another name being floated among Republicans is that of Bucks County Commissioner Michael Fitzpatrick.

The state’s deadline for candidates to withdraw from the ballot is Aug. 9, with the party required to name a substitute shortly thereafter.

Once Greenwood withdraws from the race, Democrats would also have the chance to choose a substitute candidate. While party officials said that the likelihood of a candidate swap-out is high if Greenwood exits the race, no names were immediately being floated on Monday.

In the April primary, Democrats nominated Virginia Waters Schrader, an attorney and one-time candidate for state House. Schrader had raised about $11,000 through the end of June. She had $8,000 in the bank, according to her second-quarter fundraising report, and showed about $6,000 in debt.

The race in the 8th district adds yet another high-profile contest to a state and area that already have a disproportionate number of competitive House races this cycle.

Open-seat races are under way in the 13th and 15th districts, and in the 6th district, Republican incumbent Jim Gerlach faces a race that is expected to become a top-tier contest by November.

Republicans are also gunning for Rep. Tim Holden (D) in the Harrisburg-based 17th district, but having to defend another seat in the expensive Philadelphia media market may mean that Holden’s GOP challenger, attorney Scott Paterno, gets cut out of the funding equation in the fall.

On the Hill, Greenwood’s departure will open up the chairmanship of the Energy and Commerce subcommittee on oversight and investigations, a post he has held since 2001.

His successor in that position will not be chosen until January, and it is not clear whether the oversight gavel will be taken by the current head of another subcommittee or by a rookie chairman.

The two most senior GOP members of Energy and Commerce without a subcommittee gavel are Rep. Christopher Cox (Calif.), who already chairs the Republican Policy Committee and the Homeland Security Committee, and Rep. Nathan Deal (Ga.).

As the rare moderate who has both a key committee position and the ear of Republican leaders, Greenwood has often been an important swing vote and a centrist emissary to the leadership table.

“Greenwood is a tough negotiator, but he has been a team player,” said a Republican leadership aide.

While he has been fairly conservative on economic issues, Greenwood is on the liberal end of the Republican spectrum on gun control and the environment.

Greenwood is also known as one of the most prominent House Republican backers of abortion rights. He has been a vocal supporter of funding for international family planning groups and for allowing limited types of cloning for medical research.

“He definitely carries the pro-abortion issue in the Republican Conference,” said another GOP leadership staffer.

On the Energy and Commerce Committee, Greenwood has mostly focused on consumer-related issues such as Food and Drug Administration approval of new drugs. He has also gained notice for his work on health care, Superfund reform and the investigation of Enron’s collapse.

Greenwood, the 15th House Member and 10th Republican to announce his retirement this cycle, was elected to the House in 1992 after spending six years apiece in the Pennsylvania state Assembly and Senate. Before that he was a social worker.

Brody Mullins contributed to this report.