(Reuters) - Venezuelan President Nicolas Maduro on Tuesday asked parliament for decree powers in response to new U.S. sanctions, in a move opposition critics slammed as a power-grab.

If as expected the government-controlled National Assembly approves his request for an "Enabling Law", it would be the second time the 52-year-old successor to Hugo Chavez has gained these expanded powers since winning election in 2013.

"I've come to ask for an Enabling Law to confront the aggression of the most powerful country in the world, the United States, against this beautiful nation," Maduro told parliament.

"This is a law that will prepare our country, may we never be caught off guard."

His adversaries say he is using the worst flare-up with Washington during his nearly two-year rule to justify autocratic governance, sidetrack parliament and distract attention from a shrinking economy and chronic product shortages.

"Nicolas, are you requesting the Enabling Law to make soap, nappies and medicines appear, to lower inflation?" satirized opposition leader Henrique Capriles. "It's another smokescreen."

Confirming Venezuela as Washington's No. 1 adversary in Latin America after a rapprochement with Cuba, the United States has taken its gloves off against Maduro, characterizing his government as a security threat and sanctioning seven officials.

In terminology that has also been used for measures against nations such as Iran and Syria, President Barack Obama's government declared a "national emergency" due to "the unusual and extraordinary threat" from Venezuela.



A visa ban and financial block were slapped on seven officials, ranging from the head of national intelligence and a state prosecutor to the national police chief and various military officers, for their alleged role in repressing Maduro's domestic opponents or corruption.

Maduro hailed the seven as "heroes" and named one interior minister.

Despite improving ties with Washington, communist-run Cuba was quick to join Venezuela's mockery of the U.S. language.

"Venezuela a threat to the United States? Thousands of miles away, without strategic arms and without using resources or officials to conspire against the U.S. constitutional order, the declaration is barely credible and reveals the real aims of those behind it," Cuba's government said in a statement.

Despite the diplomatic tensions, the United States is Venezuela's top trading partner, and the OPEC member's crude sales even rose in February to 796,000 barrels per day.

Venezuela's heavily traded bonds have slipped amid the dispute, with most down on Tuesday. The benchmark 2027 issue VENGLB27=RR was off 2 points, or nearly 5 percent, to a bid price of 39.444.

U.S.-Venezuelan tensions have escalated amid since Maduro's accusations that Washington was behind an alleged coup plot and the arrest of an opposition Caracas mayor accused of conspiracy.

Maduro may be calculating that nationalist sentiment will rally strained support among the traditional "Chavista" power-base of Venezuela's poor, and unite ruling Socialist Party factions ahead of a parliamentary election later this year.

Opposition legislator Elias Matta accused the government of using the U.S. spat as an excuse to ask for decree powers they had long planned to request due to fear of losing control of the National Assembly as some pollsters say they might.

"The government is taking advantage of this situation with the United States ... they'd already planned this," he said. "But a majority-led assembly can also strike down laws."

The opposition coalition, too, is seeking to unite its fractious parties and portray recent events as evidence of Maduro's dictatorial face and lack of attention to shortages, crime and other day-to-day problems.

Venezuela's National Assembly, which requires two votes to approve the Enabling Law once a formal request is received, was due to meet later on Tuesday. In the past, both Maduro and Chavez have received speedy approval of the Enabling Law.