Delivering the most important speech of his life before a packed auditorium on Thursday, Kerry, however served notice that if he defeats President George Bush in November he will not flinch from going into battle alone if necessary to protect the country.
The veteran Massachusetts senator rapped the Republican administration as a rich man's club that flouted civil rights and bent military intelligence to its political end.
"I will be a commander in chief who will never mislead us into war. I will have a Vice President who will not conduct secret meetings with polluters to rewrite our environmental laws," Kerry said.
"I will be a commander in chief who will never mislead us into war. I will have a Vice President who will not conduct secret meetings with polluters to rewrite our environmental laws"
Democratic presidential challenger
"And I will appoint an attorney general who actually upholds the constitution of the United States," he told some 20,000 cheering delegates and guests at the end of the four-day Democratic convention.
"As a president, I will restore trust and credibility to the White House."
Kerry kept his focus on security issues, pledging to beef up the US military to counter Republican charges he was weak and waffling on defence.
"Let there be no mistake: I will never hesitate to use force when it is required," Kerry said, adding he would take the country into war only to meet a "real and imminent" threat.
The Democratic presidential nominee also vowed to win back allies for the fight against terrorism, but made it clear he was ready for unilateral action if needed.
"I will never give any nation or international institution a veto over our national security," he said.
On the domestic front, Kerry lambasted Bush over the loss of US jobs, rising health-care costs and lagging educational opportunities for many people.
"America can do better. So tonight we say: help is on the way," Kerry said.