The Obama administration is seeking to rebuild diplomatic bridges in Latin America that became a casualty of the U.S. preoccupation with the Middle East or were downgraded or severed over regional tensions.

Within sight of Washington's diplomatic brokers in the region are countries that have poor U.S. official representation -- the result of past diplomatic tiffs or populist or radical policies pursued by their present or past leaders.

It's an uphill task, analysts said. A past geopolitical shift in emphasis in U.S. international relations means that some of the largest potential markets and major population centers in the region have no U.S. proactive representatives, except for commercial concerns waving the U.S. flag as best as possible.

Some of the past diplomatic cutbacks have prompted Chinese, Russian and European initiatives that have led to contracts or diplomatic exchanges materializing outside the scope of Washington.

State Department spokeswoman Victoria Nuland said the United States continues to talk with Bolivia, Ecuador and Venezuela, countries where it has no ambassadors, in an attempt to normalize relations.

"We continue to talk to all of these countries about what it would take to get back to normal relationship at the level of ambassador and to work on it," Nuland said.

However, Nuland indicated the Obama administration was applying different approaches to different countries.

The picture isn't monochromatic in the different countries, Nuland said.

"For example, in the case of Bolivia, we would like to get to a better place. In the case of Venezuela, the issue is more difficult, as you know," she said, citing a continuing row with Caracas over the appointment of a U.S. envoy there.

"These countries are different, the relationship is different, the reasons that we ended up in the posture that we're in are different," Nuland said.

"So we will approach each relationship on its merits and continue the dialogue and being very open and transparent about what it'll take, from our perspective," Nuland added.

U.S.-Venezuela relations touched a new low in September 2008 when Caracas broke off diplomatic relations with Washington.

The relations showed signs of improvement in 2009 with the election of U.S. President Barack Obama that led to a re-establishment of diplomatic relations in June 2009. But the row over envoys continues and the diplomatic ties are in a state of limbo.

Tensions over Bolivian drug policies continue to affect ties with Washington, despite a healthy in-bound U.S. tourism and a 13,000-strong American community in the country. The U.S. Embassy in La Paz has been without an ambassador since Philip S. Goldberg was expelled in September 2008.

Ecuador reacted angrily to a WikiLeaks U.S. diplomatic cable criticizing President Rafael Correa. The resulting row led to both sides expelling each other's ambassadors.