U.S. President Barack Obama is extending his lead over Republican Mitt Romney in the race for the White House.

Reuters/Ipsos poll showed Tuesday that independent voters and some optimism over the economy helped Obama extend his lead by seven points.

With six months to go before election day, Obama is backed by 49 percent of registered voters compared with 42 percent over his likely rival in November's presidential election.

Obama's overall approval rating also edged up to 50 percent, but some 47 percent of the people polled disapprove of how Obama handles his presidency.

At a campaign stop in Michigan, Romney targeted Obama's record.

(SOUNDBITE) (English) REPUBLICAN CANDIDATE MITT ROMNEY SAYING :

"The lessons of the last four years teach us a great deal about the next four years. If we continue in the same direction with the same President. We must not. It's time to bring America back."

Although Romney has effectively clinched the Republican nomination, voters in Indiana, North Carolina and West Virginia went to the polls for their scheduled primaries.

Deborah Lutterbeck, Reuters