WASHINGTON -- Democrat Barack Obama on Wednesday was showcasing his plans to encourage Americans to serve at home and abroad to address issues such as education and climate change if he is elected president. Republican John McCain was traveling through Colombia and Mexico, where he was promoting politically risky free trade.

Obama's plan, which would include doubling the size of the Peace Corps, is part of an overall agenda to press Americans into service to show "the world the best of our nation," according a statement from his campaign. He announced the plan in December, several months before he wrapped up his party's nomination.

The Democrat has spent recent days speaking out on issues that would foster a middle-of-the road political persona to counter Republican attempts to label him as too liberal. McCain, meanwhile, has sought to highlight his perceived strengths -- long experience in military and national security matters.

Obama has focused this week root ideals of American citizenship -- patriotism and service to others -- in advance of U.S. Independence Day on Friday. On Monday he defended his own patriotism and a day later promised to engage grass roots religious groups with federal money if they tackle the country's social ills.

His appearance Wednesday in Colorado Springs, Colorado, a conservative city and home to the U.S. Air Force Academy, was expected to reinforce those themes.

"Senator Obama will lay out his comprehensive national service agenda, which will create new opportunities for Americans to serve and direct that service to our most pressing national challenges," his campaign said. Obama has already promised college tuition grants to those who commit to national service after graduation.

McCain, meanwhile, praised Colombian President Alvaro Uribe's efforts to stabilize the country and reduce the flow of drugs into the United States; He said Plan Colombia, a program the U.S. government launched 10 years ago to reduce cocaine production in the country. The program and other efforts, he said, had substantially curbed cocaine supplies and raised the price of the drug on U.S. streets.

The Arizona senator also is a strong supporter of a proposed free trade agreement between the U.S. and Colombia and planned to promote it and other hemispheric trade deals during the visit. Obama opposes the Colombian agreement, which has stalled in the House over concerns about continuing intimidation and violence against labor leaders in the country.

Obama has also vowed to re-negotiate the North American Free Trade Agreement with Mexico and Canada, a deal critics say is responsible for the disappearance of American jobs. McCain supports the pact while acknowledging it is a tough sell in important U.S. states like Ohio, Pennsylvania and Michigan that have been particularly hard hit by the loss of manufacturing jobs.

In the run-up to America's national day Friday, Obama drew unexpected attention when he said in Zanesville, Ohio, he would expand federal payments to religious groups that are tackling America's social problems -- a position that could alienate some in his Democratic base who see the move as an abrogation of the country's constitutional separation of church and state.

Obama has also staked out other positions that may appeal more to independent and centrist voters, recently criticizing a Supreme Court decision that struck down a state death penalty law for child rapists and supporting the high court's reversal of a gun law ban.

Taken as a whole, the positions suggest Obama may see the possibility of picking up some conservative evangelical Christian voters.

"We know that faith and values can be a source of strength in our own lives," Obama said during a visit to the Eastside Community Ministry in Zanesville. The ministry an arm of Central Presbyterian Church that operates a food bank, provides clothes, has a youth ministry and offers other services to the poor in the central Ohio city.

"That's what it's been to me. And that's what it is to so many Americans. But it can also be something more. It can be the foundation of a new project of American renewal. And that's the kind of effort I intend to lead as President of the United States."

Obama said he would not withhold federal money from religious organizations that restrict hiring to members of that particular faith, so long as there was no such discrimination in employing workers specifically involved in programs funded by Washington.

Rev. Barry Lynn, executive director of Americans United for Separation of Church and State, said Obama's plan would only expand programs that he said undermined civil rights and civil liberties.

"I am disappointed that any presidential candidate would want to continue a failed policy of the Bush administration," he said. "It ought to be shut down, not continued."

For McCain, his first topics of discussion upon arriving in Colombia on Tuesday night were human rights and the drug trade.

"I've been a supporter of human rights for my entire life and career," McCain said after a nearly two-hour meeting with Uribe at the president's seaside mansion in Cartagena. "We have discussed this issue with President Uribe and will continue to urge progress in that direction. I believe progress is being made and that more progress needs to be made."

On Wednesday, he was to meet with other government officials and business leaders, and a tour of a Naval base before departing for Mexico City in the evening.