The Obama campaign launched an early effort Monday to discredit Mitt Romney’s upcoming overseas trip, challenging the presumptive Republican nominee to lay out specifics of his foreign policy platform in areas where he disagrees with President Obama.

Romney leaves later this week for visits to Britain, Israel and Poland aimed at projecting the aura of a statesman to convince voters he would make a plausible commander-in-chief. But in a conference call with reporters, Obama’s surrogates said Romney must do more than meet with high-level officials and appear at high-profile events, such as a scheduled appearance at Friday’s opening ceremonies of the London Summer Olympics.

“He needs to prove his worthiness in having a substantive discussion other than just generalities and soundbites in this campaign,” said Robert Gibbs, Obama’s former press secretary and a consultant working with the campaign. “Romney owes it to the American people to say where he stands on important issues as he tries out to be leader of the free world.”

The attacks drew a sharp response from the Romney campaign, which distributed an e-mail criticizing Obama’s 2008 overseas tour, while running for office, as a political gambit to raise campaign cash. And they accused the president of ignoring the deteriorating security situation in Syria in favor of campaigning this year.

“In no region of the world is our country’s influence any stronger than it was four years ago,” Romney spokesman Ryan Williams said. “President Obama has failed to restore our economy, is weakening our military with devastating defense cuts, and has diminished our moral authority.”

Romney and Obama are scheduled to speak on foreign policy today at the Veterans of Foreign Wars convention in Reno, Nev.

The Obama campaign is hoping to pressure Romney to wade deeper into complicated foreign policy questions, such as his criticism of the White House’s handling of Iran’s nuclear weapons ambitions and its timeline for removing American troops from Afghanistan in 2014.

Obama has touted his foreign policy achievements as he makes his case to voters, emphasizing that his administration has ended the war in Iraq and killed Al Qaeda chief Osama bin Laden. The president has maintained a higher approval rating on foreign policy than on his handling of the domestic economy, and the Obama campaign hopes that success will help the president rack up votes in an area where Republicans have traditionally fared strongly.

Romney, though, has been critical of Obama’s foreign policy record, saying the president has been too lenient in its sanctions policy with Iran and not strong enough in defending Israel’s security. He has called the administration’s attempt to “reset” relations with Russia a failure, coming at the expense of Eastern European allies, a point he is likely to accentuate in Poland.

In March, Romney called Russia “our No. 1 geopolitical foe,” a position that Obama’s surrogates have mocked.

“Will Romney repeat that rhetoric when he lands in Warsaw?” asked Michelle Flournoy, Obama’s former under secretary of defense for policy.

Colin Kahl, former deputy assistant secretary of defense for the Middle East, noted that Romney, while addressing a conservative Christian conference last month, stated he would do the “opposite” of Obama when it comes to dealing with Iran’s nuclear threat and Israel’s security.

“He’s almost sounded like he’s more frightened that Israel might take military action than he’s concerned that Iran might become nuclear,” Romney said while addressing the Faith and Freedom Coalition.

Romney is hoping to appeal to Jewish voters and donors in the United States by exploiting Obama’s at-times rocky relationship with Israeli Prime Minister Benjamin Netanyahu, with whom Romney developed a friendship in the 1970s when both were working as corporate advisers. Obama has yet to visit Israel while in office, a point Romney’s trip will accentuate, although Obama visited during his 2008 campaign tour.

Kahl said Romney needs to explain what he means by doing the opposite of Obama on Israel.

“If we take governor Romney at his word, that would mean doing the opposite of record high-level security funding, doing the opposite of the Iron Dome [missile defense] system that has saved Israeli lives, the opposite of standing up for Israel at the U.N., the opposite of personally intervening to save Israeli diplomats at the Cairo Embassy,” Kahl said. “Would he really do the opposite of all those things?”