Norfolk, Virginia: John McCain has earned the backing of one-time rival Fred Thompson, support that could be important in helping the likely Republican presidential nominee win backing from conservatives who have so far been wary of his candidacy.

McCain, the veteran senator who is all-but-assured the Republican nomination after chief rival Mitt Romney suspended his campaign on Thursday, also sought to play up his national security and foreign policy experience by casting himself as someone who would protect the US from terrorism.

The pitch has helped him make inroads with conservatives who form the base of the party's constituency and view him as a maverick on key issues like immigration and campaign finance reform. It also comes after Romney, in explaining his decision, said he feared his continued candidacy would work against the party and help Democrats win the presidency. Such a development, he said, would be like surrendering to terror.