U.S. President Barack Obama and Republican candidate Mitt Romney take their campaigns to the key political battleground state of Ohio Tuesday, as they seek to win over voters with four weeks left before the election.

The latest polls indicate the two candidates are virtually tied ahead of the November 6 vote. Ohio is one of the few so-called swing states that are expected to decide who wins.

Despite losing ground in the polls to Mr. Romney following a debate on domestic policy last week, Mr. Obama told supporters at a fundraising event Monday night that he “very much” intends to win the election. He urged his backers to be “almost obsessive” in their efforts until election day.

Earlier Monday, Mr. Romney accused the president of being a weak leader, especially with regard to the Middle East.

In his first major foreign policy speech of the campaign, Mr. Romney said that under President Obama, the United States is at the mercy of events rather than using what the challenger called its “great power to shape history.”

He accused the president of failing to lead in Syria, called the U.S. withdrawal of forces from Iraq “abrupt,” and said the United States and Israel are growing apart, which he says has emboldened Iran.

Mr. Romney also said there will be no flexibility with Russia on missile defense in Europe.

The Obama campaign swiftly responded to the Romney speech, saying there is a good reason the president leads Mr. Romney in the polls on national security. It cited the end to the war in Iraq and the killing of al-Qaida chief Osama bin Laden.

The two candidates are set to hold a second debate next week with citizens posing questions on both domestic and foreign issues. A third debate, focusing on foreign policy, will take place later this month.

Vice President Joe Biden and Mr. Romney's running mate, Paul Ryan, will debate Thursday.