Gran Tierra Energy to Expand Exploration Portfolio in Peru

Acquires an interest in 6.7 million gross acres in three contiguous blocks adjacent to Gran Tierra Energy's blocks 122 and 128

CALGARY, Sept. 20 /PRNewswire-FirstCall/ - Gran Tierra Energy Inc. ("Gran Tierra Energy") (NYSE Amex: GTE, TSX: GTE), a company focused on oil and gas exploration and production in South America, today announced it has entered into an agreement to farm into 3 blocks operated by Burlington Resources Peru Limited, Sucursal Peruana, a wholly owned subsidiary of ConocoPhillips Company. Under the agreement, Gran Tierra Energy will acquire a 20% working interest in blocks 123, 124 and 129, which are located in the Maranon Basin and are contiguous to Gran Tierra Energy's blocks 122 and 128. For the purpose of enhancing the regional interpretation of the area, the terms of the transaction with ConocoPhillips include sharing technical data derived from the seismic and drilling program on Gran Tierra Energy's blocks 122 and 128.

"This farm-in opportunity will enhance Gran Tierra Energy's position within the basin and provide the opportunity to work with a premier exploration and production operator that has demonstrated technical excellence, strong project management capabilities, and a firm commitment to safety and sustainable development," said Dana Coffield, President and Chief Executive Officer of Gran Tierra Energy. "With the participation in these blocks, Gran Tierra Energy will become one of the largest onshore exploration acreage holders in Peru and be well positioned to test new potential hydrocarbon plays in the region."

Blocks 123, 124 and 129 consist of approximately 6.7 million gross acres and are positioned along the flank of the Iquitos Arch adjacent to the prolific Maranon Basin, where over 1 billion barrels of recoverable oil have been discovered to date. A 2-D seismic program is currently underway on the blocks to fulfill the second period work program commitments and is scheduled for completion in 2011.

The transaction is subject to PeruPetro S.A. and Peruvian Government approvals, which are expected to take approximately four to six months.

About Gran Tierra Energy Inc.

Gran Tierra Energy is an international oil and gas exploration and production company, headquartered in Calgary, Canada, incorporated in the United States, trading on the NYSE Amex Exchange (GTE) and the Toronto Stock Exchange (GTE), and operating in South America. Gran Tierra Energy holds interests in producing and prospective properties in Argentina, Colombia, Peru, and Brazil. Gran Tierra Energy has a strategy that focuses on establishing a portfolio of producing properties, plus production enhancement and exploration opportunities to provide a base for future growth.

Gran Tierra Energy's Securities and Exchange Commission filings are available on a web site maintained by the Securities and Exchange Commission at http://www.sec.gov and on SEDAR at http://www.sedar.com.

Forward Looking Statements:

This news release contains certain forward-looking information and forward-looking statements (collectively, "forward-looking statements") under the meaning of applicable securities laws, including Canadian Securities Administrators' National Instrument 51-102 - Continuous Disclosure Obligations and the United States Private Securities Litigation Reform Act of 1995. The use of the words "scheduled", "expected" and "will" identify forward-looking statements. In particular, but without limiting the foregoing, this news release contains forward-looking statements regarding Gran Tierra Energy's planned and expected presence in Peru, as well as expected plans, results and benefits regarding commitments and exploration, production and development for the ConocoPhillips farm-in and expectations respecting the approval of PeruPetro S.A.

The forward-looking statements contained in this news release are subject to risks, uncertainties and other factors that could cause actual results or outcomes to differ materially from those contemplated by the forward-looking statements, including, among others: the transaction is subject to regulatory approval, the timing and results of which are outside of Gran Tierra Energy's control, which approval if not obtained or delayed could cause the transaction not to occur; unexpected technical difficulties and operational difficulties may occur, which could impact or delay the completion of the 2-D seismic program on the blocks; geographic, political and weather conditions can impede testing, which could impact or delay the completion of the 2-D seismic program on the blocks; and the risk that current global economic and credit market conditions may impact oil prices and oil consumption more than Gran Tierra Energy currently predicts, which could cause Gran Tierra Energy to modify its intention to expand its presence in Peru. Further information on potential factors that could affect Gran Tierra Energy are included in risks detailed from time to time in Gran Tierra Energy's Securities and Exchange Commission filings, including, without limitation, under the caption "Risk Factors" in Gran Tierra Energy's Quarterly Report on Form 10-Q filed August 6, 2010. These filings are available on a Web site maintained by the Securities and Exchange Commission at http://www.sec.gov and on SEDAR at www.sedar.com. The forward-looking statements contained herein are expressly qualified in their entirety by this cautionary statement. The forward-looking statements included in this press release are made as of the date of this press release and Gran Tierra Energy disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as expressly required by applicable securities legislation.

SOURCE Gran Tierra Energy Inc.