The following represents a (complete) conversion list of FIPS-10 to ISO-3166 country codes. It is based upon http://opengeocode.org/download/fips2iso.txt.
I have removed identical codes and updated some relations. In case you find an error please leave a comment.
AG => DZ,
AQ => AS,
AN => AD,
AV => AI,
AY => AQ,
AC => AG,
AA => AW,
AS => AU,
AU => AT,
AJ => AZ,
BF => BS,
BA => BH,
FQ => UM,
BG => BD,
BS => TF,
BO => BY,
BH => BZ,
BN => BJ,
BD => BM,
BL => BO,
BQ => AN,
BK => BA,
BC => BW,
VI => VG,
BX => BN,
BU => BG,
UV => BF,
BM => MM,
BY => BI,
CB => KH,
CJ => KY,
CT => CF,
CD => TD,
CI => CL,
CH => CN,
KT => CX,
CK => CC,
CN => KM,
CG => CD,
CF => CG,
CW => CK,
CR => AU,
CS => CR,
IV => CI,
UC => CW,
EZ => CZ,
DA => DK,
DO => DM,
DR => DO,
ES => SV,
EK => GQ,
EN => EE,
EU => TF,
FG => GF,
FP => PF,
FS => TF,
GB => GA,
GA => GM,
GZ => PS,
GG => GE,
GM => DE,
GO => TF,
GJ => GD,
GQ => GU,
GK => GG,
GV => GN,
PU => GW,
HA => HT,
VT => VA,
HO => HN,
HQ => UM,
IC => IS,
IZ => IQ,
EI => IE,
IS => IL,
JN => SJ,
JA => JP,
DQ => UM,
JQ => UM,
JU => TF,
KQ => UM,
KR => KI,
KN => KP,
KS => KR,
KU => KW,
LG => LV,
LE => LB,
LT => LS,
LI => LR,
LS => LI,
LH => LT,
MC => MO,
MA => MG,
MI => MW,
MW => ME,
RM => MH,
MB => MQ,
MP => MU,
MF => YT,
MQ => UM,
MN => MC,
MG => MN,
MJ => ME,
MH => MS,
MO => MA,
WA => NA,
BQ => UM,
NU => NI,
NG => NE,
NI => NG,
NE => NU,
CQ => MP,
MU => OM,
PS => PW,
LQ => UM,
PM => PA,
PP => PG,
PA => PY,
RP => PH,
PC => PN,
PO => PT,
RQ => PR,
RW => RE,
RS => RU,
SR => RS,
TB => BL,
SC => KN,
ST => LC,
RN => MF,
SB => PM,
TP => ST,
SG => SN,
RI => RS,
SE => SC,
SN => SG,
NN => SX,
LO => SK,
BP => SB,
SF => ZA,
SX => GS,
SP => ES,
CE => LK,
SU => SD,
NS => SR,
SV => SJ,
WZ => SZ,
SW => SE,
SZ => CH,
TC => AE,
TI => TJ,
TT => TL,
TO => TG,
TL => TK,
TN => TO,
TD => TT,
TE => TF,
TS => TN,
TU => TR,
TX => TM,
TK => TC,
UP => UA,
UK => GB,
NH => VU,
VM => VN,
VQ => VI,
WQ => UM,
WE => PS,
WI => EH,
YM => YE,
ZA => ZM,
ZI => ZW