By Deisy Buitrago, Vivian Sequera and Matt Spetalnick

CARACAS/WASHINGTON (Reuters) - Venezuela's government and its political opposition on Tuesday agreed to electoral guarantees for 2024 presidential elections, paving the way for possible U.S. sanctions relief, though the deal did not lift bans on opposition candidates barred from public office.

The elections will take place in the second half of next year, and international observers - including from the European Union and United Nations - will oversee the vote, according to terms unveiled following a resumption of long-suspended talks.

Multiple sources had said ahead of Tuesday's announcement that the U.S. was prepared to ease some oil-related sanctions on OPEC member-nation Venezuela if Washington was satisfied President Nicolas Maduro had given enough ground to the opposition.

President Joe Biden's administration had said it would lift some long-standing punitive measures in exchange for democratic concessions from Maduro.

But as the White House studied the details of the agreement finalized in Barbados, it was unclear how soon the U.S. might act or how far it could go with sanctions relief.

"We welcome the Venezuelan-led political agreement reached today in Barbados," according to a joint statement from the U.S., EU, Britain and Canada, calling it a necessary step toward the "restoration of democracy in Venezuela."

However, the statement also reiterated calls for release of political prisoners, independence of the electoral process, freedom of expression and respect for human rights, issues that were not covered in Tuesday's agreement.

Any significant alleviation of oil sanctions would mark a further shift by the Biden administration away from former President Donald Trump's "maximum pressure" campaign against the socialist-led South American country.

But U.S. sources have said any U.S. policy changes would be reversible if Maduro failed to meet his election commitments. Oil revenues are crucial to Venezuela's crippled economy.

BANNED CANDIDATES

Tuesday's meeting in Barbados, brokered by Norway, was the first between the two sides in 11 months.

The talks, meant to provide a way out of Venezuela's long-running political and economic crisis, will continue at an unspecified date, the parties said, adding they are committed to respecting the results of the vote.

The deal says each side can choose its 2024 candidate according to its internal rules, but did not reverse bans on some opposition figures - including Oct. 22 primary frontrunner Maria Corina Machado - that prevent them from holding office.

The opposition has said the bans, handed down by the controller general, are unlawful and Washington has rejected any roadblocks to opposition candidates.

"If you have an administrative inhabilitation...from the controller general of the republic you cannot be a candidate, I want to clarify that," Jorge Rodriguez, the head of the government delegation told a press conference after the signing.

Speaking before Rodriguez, the head of the opposition delegation Gerardo Blyde had said the deal could allow banned candidates to "recover their rights."

The opposition has shied away from laying out what could happen if Machado were to win the primary but could not register for the general election.

It remains unclear whether the often-fractious opposition would accept her choosing another candidate to run in her stead.

At least two candidates who initially had been set to run in the primary have bowed out because they are banned.

Maduro, president since 2013, is expected to run for re-election but has not yet formalized his candidacy.

The U.S. imposed sanctions on Venezuela to punish Maduro's government following a 2018 election that Washington considered a sham. Since 2019, U.S. sanctions have banned PDVSA from exporting its oil to its chosen markets.

The other accord signed by the two sides includes an agreement to protect Houston-based oil refiner Citgo Petroleum, whose parent company's shares will be put for auction starting this month through a court-organized process to pay creditors.