Exhibit 10(a) [LETTERHEAD OF GAFFNEY, CLINE & ASSOCIATES, INC.] ID/lmn/C599.00/2755 June 28, 2002 CONSENT OF GAFFNEY, CLINE & ASSOCIATES, INC. As independent reserve engineers for Petrolera Brasileiro S.A.'s (Petrobras), Gaffney, Cline & Associates, Inc. (GCA) hereby confirms that it has granted and not withdrawn its consent to the reference to GCA's review and certification of Petrobras' domestic reserves for the years ending December 31, 1999 and December 31, 2000 as disclosed by Petrobras in its Report 20-F to the United States Securities and Exchange Commission dated June 28, 2002. Very truly yours, GAFFNEY, CLINE & ASSOCIATES, INC. /s/ IAN DUNDERDALE Ian Dunderdale Regional Manager Americas